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	$242.42	5.765%	$256.3955	$256.40	$256.40	$256.40
Purchase #2	$36.67	10.387%	$40.4789	$40.48	$40.50	$40.50
Purchase #3	$56.36	5.105%	$59.2372	$59.24	$59.25	$59.20
Purchase #4	$157.40	9.781%	$172.7953	$172.80	$172.80	$172.80
Purchase #5	$238.53	12.201%	$267.633	$267.63	$267.65	$267.60
Purchase #6	$205.87	10.842%	$228.1904	$228.19	$228.20	$228.20
Purchase #7	$95.27	5.644%	$100.647	$100.65	$100.65	$100.60
7 purchase totals =	$1,032.52		$1,125.3773	$1,125.39	$1,125.45	$1,125.30