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	$236.57	10.146%	$260.5724	$260.57	$260.55	$260.60
Purchase #2	$41.81	8.792%	$45.4859	$45.49	$45.50	$45.50
Purchase #3	$88.95	11.317%	$99.0165	$99.02	$99.00	$99.00
Purchase #4	$66.39	8.184%	$71.8234	$71.82	$71.80	$71.80
Purchase #5	$84.87	12.284%	$95.2954	$95.30	$95.30	$95.30
Purchase #6	$222.68	12.630%	$250.8045	$250.80	$250.80	$250.80
Purchase #7	$220.74	9.643%	$242.026	$242.03	$242.05	$242.00
7 purchase totals =	$962.01		$1,065.0241	$1,065.03	$1,065.00	$1,065.00