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	$82.34	12.500%	$92.6325	$92.63	$92.65	$92.60
Purchase #2	$102.72	12.386%	$115.4429	$115.44	$115.45	$115.40
Purchase #3	$57.36	4.276%	$59.8127	$59.81	$59.80	$59.80
Purchase #4	$155.84	9.836%	$171.1684	$171.17	$171.15	$171.20
Purchase #5	$148.28	3.579%	$153.5869	$153.59	$153.60	$153.60
Purchase #6	$12.33	12.458%	$13.8661	$13.87	$13.85	$13.90
Purchase #7	$178.50	12.487%	$200.7893	$200.79	$200.80	$200.80
7 purchase totals =	$737.37		$807.2988	$807.30	$807.30	$807.30