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	$198.97	4.700%	$208.3216	$208.32	$208.30	$208.30
Purchase #2	$132.75	4.851%	$139.1897	$139.19	$139.20	$139.20
Purchase #3	$37.25	9.732%	$40.8752	$40.88	$40.90	$40.90
Purchase #4	$129.53	12.729%	$146.0179	$146.02	$146.00	$146.00
Purchase #5	$184.90	5.156%	$194.4334	$194.43	$194.45	$194.40
Purchase #6	$130.96	5.256%	$137.8433	$137.84	$137.85	$137.80
Purchase #7	$145.76	13.514%	$165.458	$165.46	$165.45	$165.50
7 purchase totals =	$960.12		$1,032.1391	$1,032.14	$1,032.15	$1,032.10