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	$148.75	12.604%	$167.4985	$167.50	$167.50	$167.50
Purchase #2	$62.34	3.766%	$64.6877	$64.69	$64.70	$64.70
Purchase #3	$55.81	7.123%	$59.7853	$59.79	$59.80	$59.80
Purchase #4	$79.65	13.604%	$90.4856	$90.49	$90.50	$90.50
Purchase #5	$71.78	7.873%	$77.4312	$77.43	$77.45	$77.40
Purchase #6	$107.41	3.102%	$110.7419	$110.74	$110.75	$110.70
Purchase #7	$185.89	7.151%	$199.183	$199.18	$199.20	$199.20
7 purchase totals =	$711.63		$769.8132	$769.82	$769.90	$769.80