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	$46.57	13.334%	$52.7796	$52.78	$52.80	$52.80
Purchase #2	$13.73	5.456%	$14.4791	$14.48	$14.50	$14.50
Purchase #3	$55.88	7.847%	$60.2649	$60.26	$60.25	$60.30
Purchase #4	$12.35	10.745%	$13.677	$13.68	$13.70	$13.70
Purchase #5	$120.32	6.556%	$128.2082	$128.21	$128.20	$128.20
Purchase #6	$137.66	10.132%	$151.6077	$151.61	$151.60	$151.60
Purchase #7	$136.53	11.251%	$151.891	$151.89	$151.90	$151.90
7 purchase totals =	$523.04		$572.9075	$572.91	$572.95	$573.00