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	$144.36	4.637%	$151.054	$151.05	$151.05	$151.10
Purchase #2	$78.92	12.793%	$89.0162	$89.02	$89.00	$89.00
Purchase #3	$52.47	11.266%	$58.3813	$58.38	$58.40	$58.40
Purchase #4	$144.67	7.605%	$155.6722	$155.67	$155.65	$155.70
Purchase #5	$186.39	13.268%	$211.1202	$211.12	$211.10	$211.10
Purchase #6	$111.38	5.185%	$117.1551	$117.16	$117.15	$117.20
Purchase #7	$246.71	11.284%	$274.5488	$274.55	$274.55	$274.50
7 purchase totals =	$964.90		$1,056.9478	$1,056.95	$1,056.90	$1,057.00