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	$232.29	4.572%	$242.9103	$242.91	$242.90	$242.90
Purchase #2	$44.88	11.802%	$50.1767	$50.18	$50.20	$50.20
Purchase #3	$24.49	4.570%	$25.6092	$25.61	$25.60	$25.60
Purchase #4	$54.51	8.268%	$59.0169	$59.02	$59.00	$59.00
Purchase #5	$190.67	6.646%	$203.3419	$203.34	$203.35	$203.30
Purchase #6	$81.59	4.288%	$85.0886	$85.09	$85.10	$85.10
Purchase #7	$132.53	3.205%	$136.7776	$136.78	$136.80	$136.80
7 purchase totals =	$760.96		$802.9212	$802.93	$802.95	$802.90