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	$113.71	3.366%	$117.5375	$117.54	$117.55	$117.50
Purchase #2	$80.73	3.198%	$83.3117	$83.31	$83.30	$83.30
Purchase #3	$40.87	6.136%	$43.3778	$43.38	$43.40	$43.40
Purchase #4	$35.67	12.483%	$40.1227	$40.12	$40.10	$40.10
Purchase #5	$66.39	12.300%	$74.556	$74.56	$74.55	$74.60
Purchase #6	$124.45	5.355%	$131.1143	$131.11	$131.10	$131.10
Purchase #7	$243.37	5.272%	$256.2005	$256.20	$256.20	$256.20
7 purchase totals =	$705.19		$746.2205	$746.22	$746.20	$746.20