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	$71.76	5.251%	$75.5281	$75.53	$75.55	$75.50
Purchase #2	$210.67	5.645%	$222.5623	$222.56	$222.55	$222.60
Purchase #3	$84.81	10.502%	$93.7167	$93.72	$93.70	$93.70
Purchase #4	$173.82	10.145%	$191.454	$191.45	$191.45	$191.50
Purchase #5	$24.67	7.550%	$26.5326	$26.53	$26.55	$26.50
Purchase #6	$81.85	10.567%	$90.4991	$90.50	$90.50	$90.50
Purchase #7	$94.67	10.415%	$104.5299	$104.53	$104.55	$104.50
7 purchase totals =	$742.25		$804.8227	$804.82	$804.85	$804.80