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	$97.27	7.249%	$104.3211	$104.32	$104.30	$104.30
Purchase #2	$97.29	7.156%	$104.2521	$104.25	$104.25	$104.30
Purchase #3	$209.71	8.659%	$227.8688	$227.87	$227.85	$227.90
Purchase #4	$74.36	12.301%	$83.507	$83.51	$83.50	$83.50
Purchase #5	$181.26	5.110%	$190.5224	$190.52	$190.50	$190.50
Purchase #6	$143.52	13.116%	$162.3441	$162.34	$162.35	$162.30
Purchase #7	$137.72	13.206%	$155.9073	$155.91	$155.90	$155.90
7 purchase totals =	$941.13		$1,028.7228	$1,028.72	$1,028.65	$1,028.70