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	$173.98	10.555%	$192.3436	$192.34	$192.35	$192.30
Purchase #2	$53.76	4.428%	$56.1405	$56.14	$56.15	$56.10
Purchase #3	$240.59	12.472%	$270.5964	$270.60	$270.60	$270.60
Purchase #4	$45.53	6.434%	$48.4594	$48.46	$48.45	$48.50
Purchase #5	$203.73	10.305%	$224.7244	$224.72	$224.70	$224.70
Purchase #6	$29.87	7.597%	$32.1392	$32.14	$32.15	$32.10
Purchase #7	$30.70	4.767%	$32.1635	$32.16	$32.15	$32.20
7 purchase totals =	$778.16		$856.5670	$856.56	$856.55	$856.50