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	$85.47	11.701%	$95.4708	$95.47	$95.45	$95.50
Purchase #2	$185.97	12.611%	$209.4227	$209.42	$209.40	$209.40
Purchase #3	$196.61	5.175%	$206.7846	$206.78	$206.80	$206.80
Purchase #4	$223.78	11.212%	$248.8702	$248.87	$248.85	$248.90
Purchase #5	$55.56	11.651%	$62.0333	$62.03	$62.05	$62.00
Purchase #6	$39.28	9.777%	$43.1204	$43.12	$43.10	$43.10
Purchase #7	$35.76	4.720%	$37.4479	$37.45	$37.45	$37.40
7 purchase totals =	$822.43		$903.1499	$903.14	$903.10	$903.10