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	$187.52	12.869%	$211.6519	$211.65	$211.65	$211.70
Purchase #2	$134.35	10.312%	$148.2042	$148.20	$148.20	$148.20
Purchase #3	$76.32	6.700%	$81.4334	$81.43	$81.45	$81.40
Purchase #4	$11.89	6.380%	$12.6486	$12.65	$12.65	$12.60
Purchase #5	$16.47	13.288%	$18.6585	$18.66	$18.65	$18.70
Purchase #6	$95.70	12.726%	$107.8788	$107.88	$107.90	$107.90
Purchase #7	$83.34	4.362%	$86.9753	$86.98	$87.00	$87.00
7 purchase totals =	$605.59		$667.4507	$667.45	$667.50	$667.50