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	$95.77	3.512%	$99.1334	$99.13	$99.15	$99.10
Purchase #2	$76.50	11.746%	$85.4857	$85.49	$85.50	$85.50
Purchase #3	$34.69	8.532%	$37.6498	$37.65	$37.65	$37.60
Purchase #4	$139.90	13.687%	$159.0481	$159.05	$159.05	$159.00
Purchase #5	$146.93	4.206%	$153.1099	$153.11	$153.10	$153.10
Purchase #6	$171.41	4.457%	$179.0497	$179.05	$179.05	$179.00
Purchase #7	$11.85	13.184%	$13.4123	$13.41	$13.40	$13.40
7 purchase totals =	$677.05		$726.8889	$726.89	$726.90	$726.70