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	$246.42	6.802%	$263.1815	$263.18	$263.20	$263.20
Purchase #2	$55.90	3.285%	$57.7363	$57.74	$57.75	$57.70
Purchase #3	$203.82	6.225%	$216.5078	$216.51	$216.50	$216.50
Purchase #4	$81.31	4.622%	$85.0681	$85.07	$85.05	$85.10
Purchase #5	$212.32	13.315%	$240.5904	$240.59	$240.60	$240.60
Purchase #6	$106.56	9.650%	$116.843	$116.84	$116.85	$116.80
Purchase #7	$172.83	8.342%	$187.2475	$187.25	$187.25	$187.20
7 purchase totals =	$1,079.16		$1,167.1746	$1,167.18	$1,167.20	$1,167.10