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	$140.61	5.732%	$148.6698	$148.67	$148.65	$148.70
Purchase #2	$35.56	4.166%	$37.0414	$37.04	$37.05	$37.00
Purchase #3	$32.86	12.745%	$37.048	$37.05	$37.05	$37.00
Purchase #4	$216.71	10.160%	$238.7277	$238.73	$238.75	$238.70
Purchase #5	$61.66	6.123%	$65.4354	$65.44	$65.45	$65.40
Purchase #6	$133.38	6.243%	$141.7069	$141.71	$141.70	$141.70
Purchase #7	$14.40	12.390%	$16.1842	$16.18	$16.20	$16.20
7 purchase totals =	$635.18		$684.8134	$684.82	$684.85	$684.70