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	$43.53	4.624%	$45.5428	$45.54	$45.55	$45.50
Purchase #2	$144.40	10.254%	$159.2068	$159.21	$159.20	$159.20
Purchase #3	$63.97	5.106%	$67.2363	$67.24	$67.25	$67.20
Purchase #4	$148.46	13.486%	$168.4813	$168.48	$168.50	$168.50
Purchase #5	$156.94	12.420%	$176.4319	$176.43	$176.45	$176.40
Purchase #6	$63.31	13.761%	$72.0221	$72.02	$72.00	$72.00
Purchase #7	$69.72	3.733%	$72.3226	$72.32	$72.30	$72.30
7 purchase totals =	$690.33		$761.2438	$761.24	$761.25	$761.10