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	$54.97	3.735%	$57.0231	$57.02	$57.00	$57.00
Purchase #2	$243.77	6.676%	$260.0441	$260.04	$260.05	$260.00
Purchase #3	$64.35	4.516%	$67.256	$67.26	$67.25	$67.30
Purchase #4	$146.29	5.275%	$154.0068	$154.01	$154.00	$154.00
Purchase #5	$156.26	10.646%	$172.8954	$172.90	$172.90	$172.90
Purchase #6	$91.81	9.258%	$100.3098	$100.31	$100.30	$100.30
Purchase #7	$125.96	10.821%	$139.5901	$139.59	$139.60	$139.60
7 purchase totals =	$883.41		$951.1253	$951.13	$951.10	$951.10