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	$125.67	5.128%	$132.1144	$132.11	$132.10	$132.10
Purchase #2	$74.42	8.849%	$81.0054	$81.01	$81.00	$81.00
Purchase #3	$146.36	13.118%	$165.5595	$165.56	$165.55	$165.60
Purchase #4	$5.98	8.393%	$6.4819	$6.48	$6.50	$6.50
Purchase #5	$93.83	13.521%	$106.5168	$106.52	$106.50	$106.50
Purchase #6	$185.39	6.194%	$196.8731	$196.87	$196.85	$196.90
Purchase #7	$122.56	7.663%	$131.9518	$131.95	$131.95	$132.00
7 purchase totals =	$754.21		$820.5029	$820.50	$820.45	$820.60