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	$47.72	11.284%	$53.1047	$53.10	$53.10	$53.10
Purchase #2	$100.98	11.136%	$112.2251	$112.23	$112.25	$112.20
Purchase #3	$106.49	9.380%	$116.4788	$116.48	$116.50	$116.50
Purchase #4	$70.34	11.810%	$78.6472	$78.65	$78.65	$78.60
Purchase #5	$216.66	3.336%	$223.8878	$223.89	$223.90	$223.90
Purchase #6	$32.40	6.460%	$34.493	$34.49	$34.50	$34.50
Purchase #7	$116.64	13.491%	$132.3759	$132.38	$132.40	$132.40
7 purchase totals =	$691.23		$751.2125	$751.22	$751.30	$751.20