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	$54.25	9.175%	$59.2274	$59.23	$59.25	$59.20
Purchase #2	$89.83	12.337%	$100.9123	$100.91	$100.90	$100.90
Purchase #3	$6.91	8.301%	$7.4836	$7.48	$7.50	$7.50
Purchase #4	$50.53	8.716%	$54.9342	$54.93	$54.95	$54.90
Purchase #5	$104.53	9.178%	$114.1238	$114.12	$114.10	$114.10
Purchase #6	$122.79	13.871%	$139.8222	$139.82	$139.80	$139.80
Purchase #7	$235.82	4.789%	$247.1134	$247.11	$247.10	$247.10
7 purchase totals =	$664.66		$723.6169	$723.60	$723.60	$723.50