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	$63.41	7.149%	$67.9432	$67.94	$67.95	$67.90
Purchase #2	$143.47	10.213%	$158.1226	$158.12	$158.10	$158.10
Purchase #3	$75.76	3.673%	$78.5427	$78.54	$78.55	$78.50
Purchase #4	$39.49	4.104%	$41.1107	$41.11	$41.10	$41.10
Purchase #5	$131.56	10.832%	$145.8106	$145.81	$145.80	$145.80
Purchase #6	$106.82	11.412%	$119.0103	$119.01	$119.00	$119.00
Purchase #7	$66.34	4.393%	$69.2543	$69.25	$69.25	$69.30
7 purchase totals =	$626.85		$679.7944	$679.78	$679.75	$679.70