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	$225.77	9.212%	$246.5679	$246.57	$246.55	$246.60
Purchase #2	$190.30	4.824%	$199.4801	$199.48	$199.50	$199.50
Purchase #3	$207.64	4.500%	$216.9838	$216.98	$217.00	$217.00
Purchase #4	$189.58	3.521%	$196.2551	$196.26	$196.25	$196.30
Purchase #5	$5.61	6.451%	$5.9719	$5.97	$5.95	$6.00
Purchase #6	$70.99	10.281%	$78.2885	$78.29	$78.30	$78.30
Purchase #7	$146.79	3.865%	$152.4634	$152.46	$152.45	$152.50
7 purchase totals =	$1,036.68		$1,096.0107	$1,096.01	$1,096.00	$1,096.20