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	$187.37	6.285%	$199.1462	$199.15	$199.15	$199.10
Purchase #2	$137.32	5.261%	$144.5444	$144.54	$144.55	$144.50
Purchase #3	$90.76	8.674%	$98.6325	$98.63	$98.65	$98.60
Purchase #4	$14.51	8.381%	$15.7261	$15.73	$15.75	$15.70
Purchase #5	$248.74	9.707%	$272.8852	$272.89	$272.90	$272.90
Purchase #6	$67.37	7.219%	$72.2334	$72.23	$72.25	$72.20
Purchase #7	$86.95	4.832%	$91.1514	$91.15	$91.15	$91.20
7 purchase totals =	$833.02		$894.3192	$894.32	$894.40	$894.20