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	$45.67	12.347%	$51.3089	$51.31	$51.30	$51.30
Purchase #2	$12.65	11.661%	$14.1251	$14.13	$14.15	$14.10
Purchase #3	$247.91	9.835%	$272.2919	$272.29	$272.30	$272.30
Purchase #4	$54.96	4.550%	$57.4607	$57.46	$57.45	$57.50
Purchase #5	$36.25	4.520%	$37.8885	$37.89	$37.90	$37.90
Purchase #6	$157.42	13.788%	$179.1251	$179.13	$179.15	$179.10
Purchase #7	$106.51	12.129%	$119.4286	$119.43	$119.45	$119.40
7 purchase totals =	$661.37		$731.6288	$731.64	$731.70	$731.60