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	$71.33	11.763%	$79.7205	$79.72	$79.70	$79.70
Purchase #2	$13.65	11.740%	$15.2525	$15.25	$15.25	$15.30
Purchase #3	$238.66	7.230%	$255.9151	$255.92	$255.90	$255.90
Purchase #4	$68.86	5.609%	$72.7224	$72.72	$72.70	$72.70
Purchase #5	$183.52	7.625%	$197.5134	$197.51	$197.50	$197.50
Purchase #6	$111.79	10.184%	$123.1747	$123.17	$123.15	$123.20
Purchase #7	$81.43	4.780%	$85.3224	$85.32	$85.30	$85.30
7 purchase totals =	$769.24		$829.6210	$829.61	$829.50	$829.60