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	$237.89	5.481%	$250.9288	$250.93	$250.95	$250.90
Purchase #2	$57.80	10.515%	$63.8777	$63.88	$63.90	$63.90
Purchase #3	$36.58	10.122%	$40.2826	$40.28	$40.30	$40.30
Purchase #4	$18.69	13.256%	$21.1675	$21.17	$21.15	$21.20
Purchase #5	$17.59	11.212%	$19.5622	$19.56	$19.55	$19.60
Purchase #6	$78.26	8.690%	$85.0608	$85.06	$85.05	$85.10
Purchase #7	$58.82	11.650%	$65.6725	$65.67	$65.65	$65.70
7 purchase totals =	$505.63		$546.5521	$546.55	$546.55	$546.70