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	$86.55	11.793%	$96.7568	$96.76	$96.75	$96.80
Purchase #2	$141.96	3.450%	$146.8576	$146.86	$146.85	$146.90
Purchase #3	$130.28	3.444%	$134.7668	$134.77	$134.75	$134.80
Purchase #4	$185.63	3.141%	$191.4606	$191.46	$191.45	$191.50
Purchase #5	$227.98	12.505%	$256.4889	$256.49	$256.50	$256.50
Purchase #6	$124.81	10.150%	$137.4782	$137.48	$137.50	$137.50
Purchase #7	$157.62	5.699%	$166.6028	$166.60	$166.60	$166.60
7 purchase totals =	$1,054.83		$1,130.4117	$1,130.42	$1,130.40	$1,130.60