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	$241.72	12.645%	$272.2855	$272.29	$272.30	$272.30
Purchase #2	$32.56	13.861%	$37.0731	$37.07	$37.05	$37.10
Purchase #3	$182.50	9.419%	$199.6897	$199.69	$199.70	$199.70
Purchase #4	$70.55	3.160%	$72.7794	$72.78	$72.80	$72.80
Purchase #5	$113.43	3.387%	$117.2719	$117.27	$117.25	$117.30
Purchase #6	$82.69	11.518%	$92.2142	$92.21	$92.20	$92.20
Purchase #7	$140.94	7.510%	$151.5246	$151.52	$151.50	$151.50
7 purchase totals =	$864.39		$942.8384	$942.83	$942.80	$942.90