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	$126.90	4.109%	$132.1143	$132.11	$132.10	$132.10
Purchase #2	$34.73	6.300%	$36.918	$36.92	$36.90	$36.90
Purchase #3	$99.38	11.449%	$110.758	$110.76	$110.75	$110.80
Purchase #4	$145.50	9.317%	$159.0562	$159.06	$159.05	$159.10
Purchase #5	$153.56	3.162%	$158.4156	$158.42	$158.40	$158.40
Purchase #6	$70.34	13.438%	$79.7923	$79.79	$79.80	$79.80
Purchase #7	$101.31	9.681%	$111.1178	$111.12	$111.10	$111.10
7 purchase totals =	$731.72		$788.1722	$788.18	$788.10	$788.20