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	$137.86	7.259%	$147.8673	$147.87	$147.85	$147.90
Purchase #2	$28.68	13.802%	$32.6384	$32.64	$32.65	$32.60
Purchase #3	$238.44	13.475%	$270.5698	$270.57	$270.55	$270.60
Purchase #4	$10.65	7.220%	$11.4189	$11.42	$11.40	$11.40
Purchase #5	$190.42	13.635%	$216.3838	$216.38	$216.40	$216.40
Purchase #6	$178.55	8.743%	$194.1606	$194.16	$194.15	$194.20
Purchase #7	$204.87	9.282%	$223.886	$223.89	$223.90	$223.90
7 purchase totals =	$989.47		$1,096.9248	$1,096.93	$1,096.90	$1,097.00