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	$232.59	7.681%	$250.4552	$250.46	$250.45	$250.50
Purchase #2	$48.71	6.567%	$51.9088	$51.91	$51.90	$51.90
Purchase #3	$9.82	5.811%	$10.3906	$10.39	$10.40	$10.40
Purchase #4	$140.41	13.405%	$159.232	$159.23	$159.25	$159.20
Purchase #5	$52.68	13.550%	$59.8181	$59.82	$59.80	$59.80
Purchase #6	$160.81	5.611%	$169.833	$169.83	$169.85	$169.80
Purchase #7	$137.65	9.819%	$151.1659	$151.17	$151.15	$151.20
7 purchase totals =	$782.67		$852.8036	$852.81	$852.80	$852.80