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	$210.89	4.213%	$219.7748	$219.77	$219.75	$219.80
Purchase #2	$56.84	4.421%	$59.3529	$59.35	$59.35	$59.40
Purchase #3	$124.87	5.625%	$131.8939	$131.89	$131.90	$131.90
Purchase #4	$39.72	12.114%	$44.5317	$44.53	$44.55	$44.50
Purchase #5	$141.87	10.123%	$156.2315	$156.23	$156.25	$156.20
Purchase #6	$158.46	8.475%	$171.8895	$171.89	$171.90	$171.90
Purchase #7	$244.53	5.416%	$257.7737	$257.77	$257.75	$257.80
7 purchase totals =	$977.18		$1,041.4480	$1,041.43	$1,041.45	$1,041.50