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	$111.77	3.753%	$115.9647	$115.96	$115.95	$116.00
Purchase #2	$68.68	4.848%	$72.0096	$72.01	$72.00	$72.00
Purchase #3	$166.47	4.129%	$173.3435	$173.34	$173.35	$173.30
Purchase #4	$226.51	7.576%	$243.6704	$243.67	$243.65	$243.70
Purchase #5	$7.38	4.188%	$7.6891	$7.69	$7.70	$7.70
Purchase #6	$148.53	13.420%	$168.4627	$168.46	$168.45	$168.50
Purchase #7	$40.97	10.641%	$45.3296	$45.33	$45.35	$45.30
7 purchase totals =	$770.31		$826.4696	$826.46	$826.45	$826.50