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	$89.58	4.391%	$93.5135	$93.51	$93.50	$93.50
Purchase #2	$88.59	11.137%	$98.4563	$98.46	$98.45	$98.50
Purchase #3	$210.64	3.574%	$218.1683	$218.17	$218.15	$218.20
Purchase #4	$242.46	5.418%	$255.5965	$255.60	$255.60	$255.60
Purchase #5	$30.70	6.107%	$32.5748	$32.57	$32.55	$32.60
Purchase #6	$152.34	4.186%	$158.717	$158.72	$158.70	$158.70
Purchase #7	$135.53	8.365%	$146.8671	$146.87	$146.85	$146.90
7 purchase totals =	$949.84		$1,003.8935	$1,003.90	$1,003.80	$1,004.00