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	$151.36	11.601%	$168.9193	$168.92	$168.90	$168.90
Purchase #2	$35.47	4.262%	$36.9817	$36.98	$37.00	$37.00
Purchase #3	$35.88	10.709%	$39.7224	$39.72	$39.70	$39.70
Purchase #4	$141.79	8.590%	$153.9698	$153.97	$153.95	$154.00
Purchase #5	$157.56	7.578%	$169.4999	$169.50	$169.50	$169.50
Purchase #6	$55.97	5.477%	$59.0355	$59.04	$59.05	$59.00
Purchase #7	$131.25	4.188%	$136.7468	$136.75	$136.75	$136.70
7 purchase totals =	$709.28		$764.8754	$764.88	$764.85	$764.80