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	$46.36	12.485%	$52.148	$52.15	$52.15	$52.10
Purchase #2	$116.79	6.266%	$124.1081	$124.11	$124.10	$124.10
Purchase #3	$145.44	5.166%	$152.9534	$152.95	$152.95	$153.00
Purchase #4	$63.90	13.478%	$72.5124	$72.51	$72.50	$72.50
Purchase #5	$77.62	3.193%	$80.0984	$80.10	$80.10	$80.10
Purchase #6	$140.27	5.791%	$148.393	$148.39	$148.40	$148.40
Purchase #7	$148.43	4.814%	$155.5754	$155.58	$155.60	$155.60
7 purchase totals =	$738.81		$785.7887	$785.79	$785.80	$785.80