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	$94.73	13.185%	$107.2202	$107.22	$107.20	$107.20
Purchase #2	$71.59	9.179%	$78.1612	$78.16	$78.15	$78.20
Purchase #3	$122.71	3.652%	$127.1914	$127.19	$127.20	$127.20
Purchase #4	$130.68	8.479%	$141.7604	$141.76	$141.75	$141.80
Purchase #5	$166.51	5.460%	$175.6014	$175.60	$175.60	$175.60
Purchase #6	$33.82	9.109%	$36.9007	$36.90	$36.90	$36.90
Purchase #7	$222.67	13.786%	$253.3673	$253.37	$253.35	$253.40
7 purchase totals =	$842.71		$920.2026	$920.20	$920.15	$920.30