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	$154.78	7.495%	$166.3808	$166.38	$166.40	$166.40
Purchase #2	$153.79	10.341%	$169.6934	$169.69	$169.70	$169.70
Purchase #3	$69.43	13.381%	$78.7204	$78.72	$78.70	$78.70
Purchase #4	$88.33	12.274%	$99.1716	$99.17	$99.15	$99.20
Purchase #5	$180.42	12.865%	$203.631	$203.63	$203.65	$203.60
Purchase #6	$7.59	7.361%	$8.1487	$8.15	$8.15	$8.10
Purchase #7	$11.25	4.758%	$11.7853	$11.79	$11.80	$11.80
7 purchase totals =	$665.59		$737.5312	$737.53	$737.55	$737.50