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	$58.83	10.142%	$64.7965	$64.80	$64.80	$64.80
Purchase #2	$144.50	9.415%	$158.1047	$158.10	$158.10	$158.10
Purchase #3	$136.25	10.111%	$150.0262	$150.03	$150.05	$150.00
Purchase #4	$140.77	7.675%	$151.5741	$151.57	$151.55	$151.60
Purchase #5	$121.34	7.869%	$130.8882	$130.89	$130.90	$130.90
Purchase #6	$196.75	10.206%	$216.8303	$216.83	$216.85	$216.80
Purchase #7	$37.44	8.534%	$40.6351	$40.64	$40.65	$40.60
7 purchase totals =	$835.88		$912.8551	$912.86	$912.90	$912.80