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	$119.94	9.494%	$131.3271	$131.33	$131.35	$131.30
Purchase #2	$91.55	7.453%	$98.3732	$98.37	$98.35	$98.40
Purchase #3	$218.65	4.445%	$228.369	$228.37	$228.35	$228.40
Purchase #4	$108.29	10.139%	$119.2695	$119.27	$119.25	$119.30
Purchase #5	$145.45	5.833%	$153.9341	$153.93	$153.95	$153.90
Purchase #6	$124.52	12.874%	$140.5507	$140.55	$140.55	$140.60
Purchase #7	$200.87	6.692%	$214.3122	$214.31	$214.30	$214.30
7 purchase totals =	$1,009.27		$1,086.1358	$1,086.13	$1,086.10	$1,086.20