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	$247.42	8.723%	$269.0024	$269.00	$269.00	$269.00
Purchase #2	$196.74	3.724%	$204.0666	$204.07	$204.05	$204.10
Purchase #3	$69.38	4.148%	$72.2579	$72.26	$72.25	$72.30
Purchase #4	$22.66	10.561%	$25.0531	$25.05	$25.05	$25.10
Purchase #5	$93.52	7.797%	$100.8118	$100.81	$100.80	$100.80
Purchase #6	$244.96	4.523%	$256.0395	$256.04	$256.05	$256.00
Purchase #7	$141.91	8.362%	$153.7765	$153.78	$153.80	$153.80
7 purchase totals =	$1,016.59		$1,081.0078	$1,081.01	$1,081.00	$1,081.10