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	$71.71	6.752%	$76.5519	$76.55	$76.55	$76.60
Purchase #2	$26.56	13.736%	$30.2083	$30.21	$30.20	$30.20
Purchase #3	$172.76	13.543%	$196.1569	$196.16	$196.15	$196.20
Purchase #4	$152.77	13.133%	$172.8333	$172.83	$172.85	$172.80
Purchase #5	$208.67	4.754%	$218.5902	$218.59	$218.60	$218.60
Purchase #6	$9.58	13.289%	$10.8531	$10.85	$10.85	$10.90
Purchase #7	$230.93	4.173%	$240.5667	$240.57	$240.55	$240.60
7 purchase totals =	$872.98		$945.7604	$945.76	$945.75	$945.90