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	$210.52	10.730%	$233.1088	$233.11	$233.10	$233.10
Purchase #2	$88.98	7.595%	$95.738	$95.74	$95.75	$95.70
Purchase #3	$74.98	3.154%	$77.3449	$77.34	$77.35	$77.30
Purchase #4	$5.40	11.264%	$6.0083	$6.01	$6.00	$6.00
Purchase #5	$191.86	10.190%	$211.4105	$211.41	$211.40	$211.40
Purchase #6	$105.55	5.488%	$111.3426	$111.34	$111.35	$111.30
Purchase #7	$17.52	6.242%	$18.6136	$18.61	$18.60	$18.60
7 purchase totals =	$694.81		$753.5667	$753.56	$753.55	$753.40