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	$233.64	13.522%	$265.2328	$265.23	$265.25	$265.20
Purchase #2	$190.88	7.181%	$204.5871	$204.59	$204.60	$204.60
Purchase #3	$53.85	10.457%	$59.4811	$59.48	$59.50	$59.50
Purchase #4	$17.49	11.142%	$19.4387	$19.44	$19.45	$19.40
Purchase #5	$113.53	6.419%	$120.8175	$120.82	$120.80	$120.80
Purchase #6	$130.48	9.619%	$143.0309	$143.03	$143.05	$143.00
Purchase #7	$235.49	7.750%	$253.7405	$253.74	$253.75	$253.70
7 purchase totals =	$975.36		$1,066.3286	$1,066.33	$1,066.40	$1,066.20