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	$73.26	12.199%	$82.197	$82.20	$82.20	$82.20
Purchase #2	$139.84	9.650%	$153.3346	$153.33	$153.35	$153.30
Purchase #3	$244.31	6.557%	$260.3294	$260.33	$260.35	$260.30
Purchase #4	$78.54	6.260%	$83.4566	$83.46	$83.45	$83.50
Purchase #5	$133.77	6.647%	$142.6617	$142.66	$142.65	$142.70
Purchase #6	$217.69	13.671%	$247.4504	$247.45	$247.45	$247.50
Purchase #7	$241.81	5.678%	$255.54	$255.54	$255.55	$255.50
7 purchase totals =	$1,129.22		$1,224.9697	$1,224.97	$1,225.00	$1,225.00