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	$80.95	3.205%	$83.5444	$83.54	$83.55	$83.50
Purchase #2	$152.75	12.317%	$171.5642	$171.56	$171.55	$171.60
Purchase #3	$236.54	11.679%	$264.1655	$264.17	$264.15	$264.20
Purchase #4	$210.30	3.546%	$217.7572	$217.76	$217.75	$217.80
Purchase #5	$206.84	12.861%	$233.4417	$233.44	$233.45	$233.40
Purchase #6	$10.48	9.193%	$11.4434	$11.44	$11.45	$11.40
Purchase #7	$36.89	10.456%	$40.7472	$40.75	$40.75	$40.70
7 purchase totals =	$934.75		$1,022.6636	$1,022.66	$1,022.65	$1,022.60