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	$97.47	12.597%	$109.7483	$109.75	$109.75	$109.70
Purchase #2	$93.67	6.240%	$99.515	$99.52	$99.50	$99.50
Purchase #3	$35.73	12.795%	$40.3017	$40.30	$40.30	$40.30
Purchase #4	$90.56	11.634%	$101.0958	$101.10	$101.10	$101.10
Purchase #5	$83.78	6.552%	$89.2693	$89.27	$89.25	$89.30
Purchase #6	$57.38	5.515%	$60.5445	$60.54	$60.55	$60.50
Purchase #7	$197.32	12.838%	$222.6519	$222.65	$222.65	$222.70
7 purchase totals =	$655.91		$723.1265	$723.13	$723.10	$723.10