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	$43.96	10.251%	$48.4663	$48.47	$48.45	$48.50
Purchase #2	$200.63	10.294%	$221.2829	$221.28	$221.30	$221.30
Purchase #3	$25.59	6.746%	$27.3163	$27.32	$27.30	$27.30
Purchase #4	$201.51	7.300%	$216.2202	$216.22	$216.20	$216.20
Purchase #5	$139.31	4.747%	$145.923	$145.92	$145.90	$145.90
Purchase #6	$228.87	11.707%	$255.6638	$255.66	$255.65	$255.70
Purchase #7	$77.55	7.848%	$83.6361	$83.64	$83.65	$83.60
7 purchase totals =	$917.42		$998.5086	$998.51	$998.45	$998.50