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	$137.25	11.341%	$152.8155	$152.82	$152.80	$152.80
Purchase #2	$191.74	13.165%	$216.9826	$216.98	$217.00	$217.00
Purchase #3	$154.35	11.309%	$171.8054	$171.81	$171.80	$171.80
Purchase #4	$155.39	11.571%	$173.3702	$173.37	$173.35	$173.40
Purchase #5	$48.84	3.403%	$50.502	$50.50	$50.50	$50.50
Purchase #6	$239.92	4.407%	$250.4933	$250.49	$250.50	$250.50
Purchase #7	$70.38	6.448%	$74.9181	$74.92	$74.90	$74.90
7 purchase totals =	$997.87		$1,090.8871	$1,090.89	$1,090.85	$1,090.90