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	$94.89	10.455%	$104.8107	$104.81	$104.80	$104.80
Purchase #2	$159.83	13.503%	$181.4118	$181.41	$181.40	$181.40
Purchase #3	$216.91	7.423%	$233.0112	$233.01	$233.00	$233.00
Purchase #4	$60.87	10.651%	$67.3533	$67.35	$67.35	$67.40
Purchase #5	$168.43	8.373%	$182.5326	$182.53	$182.55	$182.50
Purchase #6	$33.84	12.757%	$38.157	$38.16	$38.15	$38.20
Purchase #7	$43.39	4.187%	$45.2067	$45.21	$45.20	$45.20
7 purchase totals =	$778.16		$852.4833	$852.48	$852.45	$852.50