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	$130.27	13.490%	$147.8434	$147.84	$147.85	$147.80
Purchase #2	$131.31	10.663%	$145.3116	$145.31	$145.30	$145.30
Purchase #3	$169.32	6.624%	$180.5358	$180.54	$180.55	$180.50
Purchase #4	$154.38	12.302%	$173.3718	$173.37	$173.35	$173.40
Purchase #5	$62.26	6.816%	$66.5036	$66.50	$66.50	$66.50
Purchase #6	$220.33	4.247%	$229.6874	$229.69	$229.70	$229.70
Purchase #7	$179.47	11.793%	$200.6349	$200.63	$200.65	$200.60
7 purchase totals =	$1,047.34		$1,143.8885	$1,143.88	$1,143.90	$1,143.80