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	$131.96	4.151%	$137.4377	$137.44	$137.45	$137.40
Purchase #2	$210.97	6.849%	$225.4193	$225.42	$225.40	$225.40
Purchase #3	$144.58	5.424%	$152.422	$152.42	$152.40	$152.40
Purchase #4	$59.47	8.404%	$64.4679	$64.47	$64.45	$64.50
Purchase #5	$57.30	4.519%	$59.8894	$59.89	$59.90	$59.90
Purchase #6	$9.96	5.637%	$10.5214	$10.52	$10.50	$10.50
Purchase #7	$35.49	6.292%	$37.723	$37.72	$37.70	$37.70
7 purchase totals =	$649.73		$687.8807	$687.88	$687.80	$687.80