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	$143.40	6.625%	$152.9003	$152.90	$152.90	$152.90
Purchase #2	$184.30	10.628%	$203.8874	$203.89	$203.90	$203.90
Purchase #3	$239.69	10.464%	$264.7712	$264.77	$264.75	$264.80
Purchase #4	$11.49	12.771%	$12.9574	$12.96	$12.95	$13.00
Purchase #5	$18.41	13.672%	$20.927	$20.93	$20.95	$20.90
Purchase #6	$238.96	10.529%	$264.1201	$264.12	$264.10	$264.10
Purchase #7	$10.35	13.711%	$11.7691	$11.77	$11.75	$11.80
7 purchase totals =	$846.60		$931.3325	$931.34	$931.30	$931.40