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	$193.33	6.111%	$205.1444	$205.14	$205.15	$205.10
Purchase #2	$124.84	13.415%	$141.5873	$141.59	$141.60	$141.60
Purchase #3	$149.46	7.527%	$160.7099	$160.71	$160.70	$160.70
Purchase #4	$35.41	9.730%	$38.8554	$38.86	$38.85	$38.90
Purchase #5	$83.83	3.169%	$86.4866	$86.49	$86.50	$86.50
Purchase #6	$100.49	10.345%	$110.8857	$110.89	$110.90	$110.90
Purchase #7	$172.43	13.180%	$195.1563	$195.16	$195.15	$195.20
7 purchase totals =	$859.79		$938.8256	$938.84	$938.85	$938.90