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	$231.43	10.836%	$256.5078	$256.51	$256.50	$256.50
Purchase #2	$150.89	9.576%	$165.3392	$165.34	$165.35	$165.30
Purchase #3	$119.79	7.352%	$128.597	$128.60	$128.60	$128.60
Purchase #4	$153.89	11.322%	$171.3134	$171.31	$171.30	$171.30
Purchase #5	$243.71	9.306%	$266.3897	$266.39	$266.40	$266.40
Purchase #6	$118.72	5.375%	$125.1012	$125.10	$125.10	$125.10
Purchase #7	$242.86	5.506%	$256.2319	$256.23	$256.25	$256.20
7 purchase totals =	$1,261.29		$1,369.4802	$1,369.48	$1,369.50	$1,369.40