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	$106.69	4.512%	$111.5039	$111.50	$111.50	$111.50
Purchase #2	$61.86	5.186%	$65.0681	$65.07	$65.05	$65.10
Purchase #3	$105.56	12.796%	$119.0675	$119.07	$119.05	$119.10
Purchase #4	$175.32	11.725%	$195.8763	$195.88	$195.90	$195.90
Purchase #5	$175.50	11.778%	$196.1704	$196.17	$196.15	$196.20
Purchase #6	$157.90	5.760%	$166.995	$167.00	$167.00	$167.00
Purchase #7	$125.94	8.685%	$136.8779	$136.88	$136.90	$136.90
7 purchase totals =	$908.77		$991.5591	$991.57	$991.55	$991.70