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	$200.47	11.419%	$223.3617	$223.36	$223.35	$223.40
Purchase #2	$25.52	13.246%	$28.9004	$28.90	$28.90	$28.90
Purchase #3	$46.66	4.789%	$48.8945	$48.89	$48.90	$48.90
Purchase #4	$82.83	3.494%	$85.7241	$85.72	$85.70	$85.70
Purchase #5	$88.28	7.640%	$95.0246	$95.02	$95.00	$95.00
Purchase #6	$15.93	6.856%	$17.0222	$17.02	$17.00	$17.00
Purchase #7	$23.64	4.603%	$24.7281	$24.73	$24.75	$24.70
7 purchase totals =	$483.33		$523.6556	$523.64	$523.60	$523.60