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	$80.81	6.512%	$86.0723	$86.07	$86.05	$86.10
Purchase #2	$135.33	12.618%	$152.4059	$152.41	$152.40	$152.40
Purchase #3	$59.98	3.249%	$61.9288	$61.93	$61.95	$61.90
Purchase #4	$80.94	11.111%	$89.9332	$89.93	$89.95	$89.90
Purchase #5	$106.60	6.519%	$113.5493	$113.55	$113.55	$113.50
Purchase #6	$62.50	12.218%	$70.1363	$70.14	$70.15	$70.10
Purchase #7	$116.62	12.250%	$130.906	$130.91	$130.90	$130.90
7 purchase totals =	$642.78		$704.9318	$704.94	$704.95	$704.80