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	$44.29	3.756%	$45.9535	$45.95	$45.95	$46.00
Purchase #2	$146.74	4.818%	$153.8099	$153.81	$153.80	$153.80
Purchase #3	$133.26	10.251%	$146.9205	$146.92	$146.90	$146.90
Purchase #4	$41.34	10.281%	$45.5902	$45.59	$45.60	$45.60
Purchase #5	$82.30	3.674%	$85.3237	$85.32	$85.30	$85.30
Purchase #6	$231.73	5.553%	$244.598	$244.60	$244.60	$244.60
Purchase #7	$192.61	5.661%	$203.5137	$203.51	$203.50	$203.50
7 purchase totals =	$872.27		$925.7095	$925.70	$925.65	$925.70