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	$145.61	13.275%	$164.9397	$164.94	$164.95	$164.90
Purchase #2	$197.29	12.862%	$222.6654	$222.67	$222.65	$222.70
Purchase #3	$22.83	6.394%	$24.2898	$24.29	$24.30	$24.30
Purchase #4	$98.67	10.570%	$109.0994	$109.10	$109.10	$109.10
Purchase #5	$133.62	12.481%	$150.2971	$150.30	$150.30	$150.30
Purchase #6	$120.64	11.357%	$134.3411	$134.34	$134.35	$134.30
Purchase #7	$157.71	4.857%	$165.37	$165.37	$165.35	$165.40
7 purchase totals =	$876.37		$971.0025	$971.01	$971.00	$971.00