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	$128.26	3.154%	$132.3053	$132.31	$132.30	$132.30
Purchase #2	$177.96	7.822%	$191.88	$191.88	$191.90	$191.90
Purchase #3	$62.95	5.395%	$66.3462	$66.35	$66.35	$66.30
Purchase #4	$91.75	8.208%	$99.2808	$99.28	$99.30	$99.30
Purchase #5	$82.27	8.384%	$89.1675	$89.17	$89.15	$89.20
Purchase #6	$111.83	6.124%	$118.6785	$118.68	$118.70	$118.70
Purchase #7	$75.61	8.484%	$82.0248	$82.02	$82.00	$82.00
7 purchase totals =	$730.63		$779.6831	$779.69	$779.70	$779.70