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	$119.80	4.512%	$125.2054	$125.21	$125.20	$125.20
Purchase #2	$100.61	10.631%	$111.3058	$111.31	$111.30	$111.30
Purchase #3	$140.59	11.284%	$156.4542	$156.45	$156.45	$156.50
Purchase #4	$30.78	13.331%	$34.8833	$34.88	$34.90	$34.90
Purchase #5	$74.91	8.491%	$81.2706	$81.27	$81.25	$81.30
Purchase #6	$35.46	8.851%	$38.5986	$38.60	$38.60	$38.60
Purchase #7	$72.80	5.276%	$76.6409	$76.64	$76.65	$76.60
7 purchase totals =	$574.95		$624.3588	$624.36	$624.35	$624.40