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	$246.40	7.508%	$264.8997	$264.90	$264.90	$264.90
Purchase #2	$68.46	12.806%	$77.227	$77.23	$77.25	$77.20
Purchase #3	$112.66	9.493%	$123.3548	$123.35	$123.35	$123.40
Purchase #4	$90.35	11.201%	$100.4701	$100.47	$100.45	$100.50
Purchase #5	$10.29	7.558%	$11.0677	$11.07	$11.05	$11.10
Purchase #6	$86.48	5.226%	$90.9994	$91.00	$91.00	$91.00
Purchase #7	$229.77	6.129%	$243.8526	$243.85	$243.85	$243.90
7 purchase totals =	$844.41		$911.8713	$911.87	$911.85	$912.00