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	$172.67	12.121%	$193.5993	$193.60	$193.60	$193.60
Purchase #2	$213.50	12.840%	$240.9134	$240.91	$240.90	$240.90
Purchase #3	$99.83	3.859%	$103.6824	$103.68	$103.70	$103.70
Purchase #4	$227.41	12.679%	$256.2433	$256.24	$256.25	$256.20
Purchase #5	$80.84	13.761%	$91.9644	$91.96	$91.95	$92.00
Purchase #6	$20.49	5.790%	$21.6764	$21.68	$21.70	$21.70
Purchase #7	$165.81	13.847%	$188.7697	$188.77	$188.75	$188.80
7 purchase totals =	$980.55		$1,096.8489	$1,096.84	$1,096.85	$1,096.90