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	$229.58	10.364%	$253.3737	$253.37	$253.35	$253.40
Purchase #2	$52.68	12.664%	$59.3514	$59.35	$59.35	$59.40
Purchase #3	$248.32	3.253%	$256.3978	$256.40	$256.40	$256.40
Purchase #4	$33.26	5.269%	$35.0125	$35.01	$35.00	$35.00
Purchase #5	$183.46	4.787%	$192.2422	$192.24	$192.25	$192.20
Purchase #6	$95.98	3.644%	$99.4775	$99.48	$99.50	$99.50
Purchase #7	$159.67	3.810%	$165.7534	$165.75	$165.75	$165.80
7 purchase totals =	$1,002.95		$1,061.6085	$1,061.60	$1,061.60	$1,061.70