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	$30.76	4.594%	$32.1731	$32.17	$32.15	$32.20
Purchase #2	$68.95	10.637%	$76.2842	$76.28	$76.30	$76.30
Purchase #3	$221.71	6.840%	$236.875	$236.88	$236.90	$236.90
Purchase #4	$79.87	7.282%	$85.6861	$85.69	$85.70	$85.70
Purchase #5	$87.55	9.510%	$95.876	$95.88	$95.90	$95.90
Purchase #6	$43.30	12.584%	$48.7489	$48.75	$48.75	$48.70
Purchase #7	$179.64	3.490%	$185.9094	$185.91	$185.90	$185.90
7 purchase totals =	$711.78		$761.5527	$761.56	$761.60	$761.60