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	$61.81	4.339%	$64.4919	$64.49	$64.50	$64.50
Purchase #2	$210.87	6.185%	$223.9123	$223.91	$223.90	$223.90
Purchase #3	$73.30	11.759%	$81.9193	$81.92	$81.90	$81.90
Purchase #4	$16.94	8.327%	$18.3506	$18.35	$18.35	$18.40
Purchase #5	$171.36	9.429%	$187.5175	$187.52	$187.50	$187.50
Purchase #6	$10.81	3.535%	$11.1921	$11.19	$11.20	$11.20
Purchase #7	$112.43	9.515%	$123.1277	$123.13	$123.15	$123.10
7 purchase totals =	$657.52		$710.5114	$710.51	$710.50	$710.50