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	$103.99	6.742%	$111.001	$111.00	$111.00	$111.00
Purchase #2	$63.35	12.726%	$71.4119	$71.41	$71.40	$71.40
Purchase #3	$119.56	7.599%	$128.6454	$128.65	$128.65	$128.60
Purchase #4	$14.45	3.451%	$14.9487	$14.95	$14.95	$14.90
Purchase #5	$128.77	11.155%	$143.1343	$143.13	$143.15	$143.10
Purchase #6	$154.58	3.855%	$160.5391	$160.54	$160.55	$160.50
Purchase #7	$7.30	5.326%	$7.6888	$7.69	$7.70	$7.70
7 purchase totals =	$592.00		$637.3692	$637.37	$637.40	$637.20