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	$190.40	11.318%	$211.9495	$211.95	$211.95	$211.90
Purchase #2	$191.40	5.565%	$202.0514	$202.05	$202.05	$202.10
Purchase #3	$93.38	13.418%	$105.9097	$105.91	$105.90	$105.90
Purchase #4	$175.35	12.104%	$196.5744	$196.57	$196.55	$196.60
Purchase #5	$92.89	4.594%	$97.1574	$97.16	$97.15	$97.20
Purchase #6	$61.40	10.460%	$67.8224	$67.82	$67.80	$67.80
Purchase #7	$88.72	12.128%	$99.48	$99.48	$99.50	$99.50
7 purchase totals =	$893.54		$980.9448	$980.94	$980.90	$981.00