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	$58.41	12.375%	$65.6382	$65.64	$65.65	$65.60
Purchase #2	$179.80	10.826%	$199.2651	$199.27	$199.25	$199.30
Purchase #3	$199.81	13.810%	$227.4038	$227.40	$227.40	$227.40
Purchase #4	$186.41	13.198%	$211.0124	$211.01	$211.00	$211.00
Purchase #5	$59.90	13.172%	$67.79	$67.79	$67.80	$67.80
Purchase #6	$53.32	12.465%	$59.9663	$59.97	$59.95	$60.00
Purchase #7	$163.71	12.654%	$184.4259	$184.43	$184.45	$184.40
7 purchase totals =	$901.36		$1,015.5017	$1,015.51	$1,015.50	$1,015.50