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	$57.59	11.706%	$64.3315	$64.33	$64.35	$64.30
Purchase #2	$85.30	13.424%	$96.7507	$96.75	$96.75	$96.80
Purchase #3	$192.86	3.726%	$200.046	$200.05	$200.05	$200.00
Purchase #4	$55.77	10.358%	$61.5467	$61.55	$61.55	$61.50
Purchase #5	$239.44	11.320%	$266.5446	$266.54	$266.55	$266.50
Purchase #6	$22.95	10.158%	$25.2813	$25.28	$25.30	$25.30
Purchase #7	$37.47	7.821%	$40.4005	$40.40	$40.40	$40.40
7 purchase totals =	$691.38		$754.9013	$754.90	$754.95	$754.80