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	$51.90	13.405%	$58.8572	$58.86	$58.85	$58.90
Purchase #2	$247.88	13.546%	$281.4578	$281.46	$281.45	$281.50
Purchase #3	$224.39	11.286%	$249.7147	$249.71	$249.70	$249.70
Purchase #4	$40.42	4.438%	$42.2138	$42.21	$42.20	$42.20
Purchase #5	$30.58	4.702%	$32.0179	$32.02	$32.00	$32.00
Purchase #6	$101.47	11.438%	$113.0761	$113.08	$113.10	$113.10
Purchase #7	$55.85	6.416%	$59.4333	$59.43	$59.45	$59.40
7 purchase totals =	$752.49		$836.7708	$836.77	$836.75	$836.80