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	$124.76	5.714%	$131.8888	$131.89	$131.90	$131.90
Purchase #2	$141.48	13.253%	$160.2303	$160.23	$160.25	$160.20
Purchase #3	$130.77	12.213%	$146.7409	$146.74	$146.75	$146.70
Purchase #4	$28.88	12.556%	$32.5062	$32.51	$32.50	$32.50
Purchase #5	$166.42	9.743%	$182.6343	$182.63	$182.65	$182.60
Purchase #6	$212.34	13.125%	$240.2096	$240.21	$240.20	$240.20
Purchase #7	$139.34	4.629%	$145.79	$145.79	$145.80	$145.80
7 purchase totals =	$943.99		$1,040.0001	$1,040.00	$1,040.05	$1,039.90