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	$185.61	5.367%	$195.5717	$195.57	$195.55	$195.60
Purchase #2	$105.88	7.613%	$113.9406	$113.94	$113.95	$113.90
Purchase #3	$166.70	3.695%	$172.8596	$172.86	$172.85	$172.90
Purchase #4	$52.50	3.186%	$54.1727	$54.17	$54.15	$54.20
Purchase #5	$97.28	5.760%	$102.8833	$102.88	$102.90	$102.90
Purchase #6	$81.50	6.794%	$87.0371	$87.04	$87.05	$87.00
Purchase #7	$219.54	13.439%	$249.044	$249.04	$249.05	$249.00
7 purchase totals =	$909.01		$975.5090	$975.50	$975.50	$975.50