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	$215.81	5.590%	$227.8738	$227.87	$227.85	$227.90
Purchase #2	$186.38	7.389%	$200.1516	$200.15	$200.15	$200.20
Purchase #3	$185.73	12.551%	$209.041	$209.04	$209.05	$209.00
Purchase #4	$35.66	5.263%	$37.5368	$37.54	$37.55	$37.50
Purchase #5	$135.34	5.497%	$142.7796	$142.78	$142.80	$142.80
Purchase #6	$74.47	4.347%	$77.7072	$77.71	$77.70	$77.70
Purchase #7	$29.75	8.548%	$32.293	$32.29	$32.30	$32.30
7 purchase totals =	$863.14		$927.3830	$927.38	$927.40	$927.40