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	$17.43	11.123%	$19.3687	$19.37	$19.35	$19.40
Purchase #2	$216.52	13.837%	$246.4799	$246.48	$246.50	$246.50
Purchase #3	$232.55	5.764%	$245.9542	$245.95	$245.95	$246.00
Purchase #4	$143.37	6.571%	$152.7908	$152.79	$152.80	$152.80
Purchase #5	$148.34	5.510%	$156.5135	$156.51	$156.50	$156.50
Purchase #6	$228.71	10.456%	$252.6239	$252.62	$252.60	$252.60
Purchase #7	$28.30	12.710%	$31.8969	$31.90	$31.90	$31.90
7 purchase totals =	$1,015.22		$1,105.6279	$1,105.62	$1,105.60	$1,105.70