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	$101.33	8.433%	$109.8752	$109.88	$109.90	$109.90
Purchase #2	$58.72	13.478%	$66.6343	$66.63	$66.65	$66.60
Purchase #3	$127.83	9.158%	$139.5367	$139.54	$139.55	$139.50
Purchase #4	$234.66	11.772%	$262.2842	$262.28	$262.30	$262.30
Purchase #5	$88.87	12.128%	$99.6482	$99.65	$99.65	$99.60
Purchase #6	$147.37	9.394%	$161.2139	$161.21	$161.20	$161.20
Purchase #7	$185.33	5.818%	$196.1125	$196.11	$196.10	$196.10
7 purchase totals =	$944.11		$1,035.3050	$1,035.30	$1,035.35	$1,035.20