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	$206.88	7.227%	$221.8312	$221.83	$221.85	$221.80
Purchase #2	$12.65	8.180%	$13.6848	$13.68	$13.70	$13.70
Purchase #3	$112.76	12.119%	$126.4254	$126.43	$126.45	$126.40
Purchase #4	$82.62	9.773%	$90.6945	$90.69	$90.70	$90.70
Purchase #5	$179.57	9.642%	$196.8841	$196.88	$196.90	$196.90
Purchase #6	$141.61	7.643%	$152.4333	$152.43	$152.45	$152.40
Purchase #7	$157.95	8.725%	$171.7311	$171.73	$171.75	$171.70
7 purchase totals =	$894.04		$973.6844	$973.67	$973.80	$973.60