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	$159.85	9.635%	$175.2515	$175.25	$175.25	$175.30
Purchase #2	$244.77	8.494%	$265.5608	$265.56	$265.55	$265.60
Purchase #3	$179.26	9.848%	$196.9135	$196.91	$196.90	$196.90
Purchase #4	$111.31	6.271%	$118.2903	$118.29	$118.30	$118.30
Purchase #5	$23.43	12.434%	$26.3433	$26.34	$26.35	$26.30
Purchase #6	$121.56	9.217%	$132.7642	$132.76	$132.75	$132.80
Purchase #7	$159.78	5.733%	$168.9402	$168.94	$168.95	$168.90
7 purchase totals =	$999.96		$1,084.0638	$1,084.05	$1,084.05	$1,084.10