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	$31.63	12.362%	$35.5401	$35.54	$35.55	$35.50
Purchase #2	$148.34	11.323%	$165.1365	$165.14	$165.15	$165.10
Purchase #3	$57.29	3.534%	$59.3146	$59.31	$59.30	$59.30
Purchase #4	$226.33	12.625%	$254.9042	$254.90	$254.90	$254.90
Purchase #5	$118.38	7.756%	$127.5616	$127.56	$127.55	$127.60
Purchase #6	$157.98	11.185%	$175.6501	$175.65	$175.65	$175.70
Purchase #7	$122.59	4.575%	$128.1985	$128.20	$128.20	$128.20
7 purchase totals =	$862.54		$946.3056	$946.30	$946.30	$946.30