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	$141.67	5.143%	$148.9561	$148.96	$148.95	$149.00
Purchase #2	$55.98	6.383%	$59.5532	$59.55	$59.55	$59.60
Purchase #3	$60.53	11.854%	$67.7052	$67.71	$67.70	$67.70
Purchase #4	$196.75	7.386%	$211.282	$211.28	$211.30	$211.30
Purchase #5	$132.45	6.408%	$140.9374	$140.94	$140.95	$140.90
Purchase #6	$98.49	13.348%	$111.6364	$111.64	$111.65	$111.60
Purchase #7	$123.66	5.751%	$130.7717	$130.77	$130.75	$130.80
7 purchase totals =	$809.53		$870.8420	$870.85	$870.85	$870.90