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	$108.62	7.819%	$117.113	$117.11	$117.10	$117.10
Purchase #2	$220.63	9.151%	$240.8199	$240.82	$240.80	$240.80
Purchase #3	$172.33	13.753%	$196.0305	$196.03	$196.05	$196.00
Purchase #4	$132.57	8.298%	$143.5707	$143.57	$143.55	$143.60
Purchase #5	$154.70	12.567%	$174.1411	$174.14	$174.15	$174.10
Purchase #6	$67.74	13.534%	$76.9079	$76.91	$76.90	$76.90
Purchase #7	$92.40	11.731%	$103.2394	$103.24	$103.25	$103.20
7 purchase totals =	$948.99		$1,051.8225	$1,051.82	$1,051.80	$1,051.70