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	$58.65	5.576%	$61.9203	$61.92	$61.90	$61.90
Purchase #2	$142.38	5.150%	$149.7126	$149.71	$149.70	$149.70
Purchase #3	$37.60	7.123%	$40.2782	$40.28	$40.30	$40.30
Purchase #4	$77.77	11.507%	$86.719	$86.72	$86.70	$86.70
Purchase #5	$227.28	12.768%	$256.2991	$256.30	$256.30	$256.30
Purchase #6	$178.45	5.250%	$187.8186	$187.82	$187.80	$187.80
Purchase #7	$32.88	8.281%	$35.6028	$35.60	$35.60	$35.60
7 purchase totals =	$755.01		$818.3506	$818.35	$818.30	$818.30