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	$181.44	13.781%	$206.4442	$206.44	$206.45	$206.40
Purchase #2	$37.79	3.718%	$39.195	$39.20	$39.20	$39.20
Purchase #3	$136.54	10.190%	$150.4534	$150.45	$150.45	$150.50
Purchase #4	$180.62	10.760%	$200.0547	$200.05	$200.05	$200.10
Purchase #5	$55.70	6.344%	$59.2336	$59.23	$59.25	$59.20
Purchase #6	$92.58	11.453%	$103.1832	$103.18	$103.20	$103.20
Purchase #7	$97.34	7.146%	$104.2959	$104.30	$104.30	$104.30
7 purchase totals =	$782.01		$862.8600	$862.85	$862.90	$862.90