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	$159.83	10.443%	$176.521	$176.52	$176.50	$176.50
Purchase #2	$122.83	4.286%	$128.0945	$128.09	$128.10	$128.10
Purchase #3	$232.56	11.784%	$259.9649	$259.96	$259.95	$260.00
Purchase #4	$223.41	13.351%	$253.2375	$253.24	$253.25	$253.20
Purchase #5	$119.85	5.604%	$126.5664	$126.57	$126.55	$126.60
Purchase #6	$124.87	12.207%	$140.1129	$140.11	$140.10	$140.10
Purchase #7	$73.52	12.601%	$82.7843	$82.78	$82.80	$82.80
7 purchase totals =	$1,056.87		$1,167.2815	$1,167.27	$1,167.25	$1,167.30