Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$173.49	13.102%	$196.2207	$196.22	$196.20	$196.20
Purchase #2	$175.45	12.160%	$196.7847	$196.78	$196.80	$196.80
Purchase #3	$139.31	4.749%	$145.9258	$145.93	$145.95	$145.90
Purchase #4	$104.43	13.310%	$118.3296	$118.33	$118.35	$118.30
Purchase #5	$179.40	4.169%	$186.8792	$186.88	$186.90	$186.90
Purchase #6	$145.92	3.261%	$150.6785	$150.68	$150.70	$150.70
Purchase #7	$178.34	7.594%	$191.8831	$191.88	$191.90	$191.90
7 purchase totals =	$1,096.34		$1,186.7016	$1,186.70	$1,186.80	$1,186.70