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	$102.43	8.382%	$111.0157	$111.02	$111.00	$111.00
Purchase #2	$192.97	8.467%	$209.3088	$209.31	$209.30	$209.30
Purchase #3	$207.82	13.433%	$235.7365	$235.74	$235.75	$235.70
Purchase #4	$5.40	5.152%	$5.6782	$5.68	$5.70	$5.70
Purchase #5	$27.71	13.587%	$31.475	$31.48	$31.50	$31.50
Purchase #6	$82.59	8.439%	$89.5598	$89.56	$89.55	$89.60
Purchase #7	$31.72	12.837%	$35.7919	$35.79	$35.80	$35.80
7 purchase totals =	$650.64		$718.5659	$718.58	$718.60	$718.60