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	$82.26	12.451%	$92.5022	$92.50	$92.50	$92.50
Purchase #2	$83.43	8.275%	$90.3338	$90.33	$90.35	$90.30
Purchase #3	$235.91	5.345%	$248.5194	$248.52	$248.50	$248.50
Purchase #4	$227.92	3.761%	$236.4921	$236.49	$236.50	$236.50
Purchase #5	$85.34	4.540%	$89.2144	$89.21	$89.20	$89.20
Purchase #6	$122.37	11.229%	$136.1109	$136.11	$136.10	$136.10
Purchase #7	$94.39	9.844%	$103.6818	$103.68	$103.70	$103.70
7 purchase totals =	$931.62		$996.8546	$996.84	$996.85	$996.80