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	$62.95	7.123%	$67.4339	$67.43	$67.45	$67.40
Purchase #2	$223.37	10.457%	$246.7278	$246.73	$246.75	$246.70
Purchase #3	$223.90	6.373%	$238.1691	$238.17	$238.15	$238.20
Purchase #4	$45.94	6.360%	$48.8618	$48.86	$48.85	$48.90
Purchase #5	$221.82	8.650%	$241.0074	$241.01	$241.00	$241.00
Purchase #6	$104.74	3.238%	$108.1315	$108.13	$108.15	$108.10
Purchase #7	$126.83	11.261%	$141.1123	$141.11	$141.10	$141.10
7 purchase totals =	$1,009.55		$1,091.4438	$1,091.44	$1,091.45	$1,091.40