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	$125.73	5.260%	$132.3434	$132.34	$132.35	$132.30
Purchase #2	$214.94	4.624%	$224.8788	$224.88	$224.90	$224.90
Purchase #3	$55.42	12.103%	$62.1275	$62.13	$62.15	$62.10
Purchase #4	$59.92	4.302%	$62.4978	$62.50	$62.50	$62.50
Purchase #5	$71.88	12.750%	$81.0447	$81.04	$81.05	$81.00
Purchase #6	$39.81	12.192%	$44.6636	$44.66	$44.65	$44.70
Purchase #7	$55.74	7.488%	$59.9138	$59.91	$59.90	$59.90
7 purchase totals =	$623.44		$667.4696	$667.46	$667.50	$667.40