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	$125.54	13.774%	$142.8319	$142.83	$142.85	$142.80
Purchase #2	$94.87	3.511%	$98.2009	$98.20	$98.20	$98.20
Purchase #3	$77.56	10.794%	$85.9318	$85.93	$85.95	$85.90
Purchase #4	$90.68	4.411%	$94.6799	$94.68	$94.70	$94.70
Purchase #5	$47.95	4.547%	$50.1303	$50.13	$50.15	$50.10
Purchase #6	$19.39	7.494%	$20.8431	$20.84	$20.85	$20.80
Purchase #7	$36.84	7.327%	$39.5393	$39.54	$39.55	$39.50
7 purchase totals =	$492.83		$532.1572	$532.15	$532.25	$532.00