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	$98.75	13.669%	$112.2481	$112.25	$112.25	$112.20
Purchase #2	$242.29	12.631%	$272.8936	$272.89	$272.90	$272.90
Purchase #3	$82.54	8.735%	$89.7499	$89.75	$89.75	$89.70
Purchase #4	$32.65	8.590%	$35.4546	$35.45	$35.45	$35.50
Purchase #5	$20.35	9.631%	$22.3099	$22.31	$22.30	$22.30
Purchase #6	$59.34	3.175%	$61.224	$61.22	$61.20	$61.20
Purchase #7	$121.50	7.540%	$130.6611	$130.66	$130.65	$130.70
7 purchase totals =	$657.42		$724.5412	$724.53	$724.50	$724.50