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	$47.41	12.863%	$53.5083	$53.51	$53.50	$53.50
Purchase #2	$229.98	10.500%	$254.1279	$254.13	$254.15	$254.10
Purchase #3	$21.83	11.655%	$24.3743	$24.37	$24.35	$24.40
Purchase #4	$191.86	8.479%	$208.1278	$208.13	$208.15	$208.10
Purchase #5	$226.97	4.477%	$237.1314	$237.13	$237.15	$237.10
Purchase #6	$248.89	8.741%	$270.6455	$270.65	$270.65	$270.60
Purchase #7	$39.96	6.433%	$42.5306	$42.53	$42.55	$42.50
7 purchase totals =	$1,006.90		$1,090.4458	$1,090.45	$1,090.50	$1,090.30