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	$92.83	4.763%	$97.2515	$97.25	$97.25	$97.30
Purchase #2	$230.79	4.245%	$240.587	$240.59	$240.60	$240.60
Purchase #3	$201.67	10.844%	$223.5391	$223.54	$223.55	$223.50
Purchase #4	$171.62	13.422%	$194.6548	$194.65	$194.65	$194.70
Purchase #5	$238.42	13.165%	$269.808	$269.81	$269.80	$269.80
Purchase #6	$73.33	7.330%	$78.7051	$78.71	$78.70	$78.70
Purchase #7	$158.93	4.102%	$165.4493	$165.45	$165.45	$165.40
7 purchase totals =	$1,167.59		$1,269.9948	$1,270.00	$1,270.00	$1,270.00