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	$56.81	5.296%	$59.8187	$59.82	$59.80	$59.80
Purchase #2	$207.44	5.677%	$219.2164	$219.22	$219.20	$219.20
Purchase #3	$134.44	13.747%	$152.9215	$152.92	$152.90	$152.90
Purchase #4	$153.35	12.479%	$172.4865	$172.49	$172.50	$172.50
Purchase #5	$124.96	4.192%	$130.1983	$130.20	$130.20	$130.20
Purchase #6	$57.32	3.858%	$59.5314	$59.53	$59.55	$59.50
Purchase #7	$229.42	10.587%	$253.7087	$253.71	$253.70	$253.70
7 purchase totals =	$963.74		$1,047.8815	$1,047.89	$1,047.85	$1,047.80