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	$196.41	10.760%	$217.5437	$217.54	$217.55	$217.50
Purchase #2	$165.76	10.204%	$182.6742	$182.67	$182.65	$182.70
Purchase #3	$155.25	6.821%	$165.8396	$165.84	$165.85	$165.80
Purchase #4	$152.58	12.698%	$171.9546	$171.95	$171.95	$172.00
Purchase #5	$10.28	6.170%	$10.9143	$10.91	$10.90	$10.90
Purchase #6	$129.45	9.579%	$141.85	$141.85	$141.85	$141.90
Purchase #7	$82.26	11.665%	$91.8556	$91.86	$91.85	$91.90
7 purchase totals =	$891.99		$982.6320	$982.62	$982.60	$982.70