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	$125.74	13.211%	$142.3515	$142.35	$142.35	$142.40
Purchase #2	$165.84	11.688%	$185.2234	$185.22	$185.20	$185.20
Purchase #3	$182.46	11.700%	$203.8078	$203.81	$203.80	$203.80
Purchase #4	$87.98	13.183%	$99.5784	$99.58	$99.60	$99.60
Purchase #5	$69.85	11.688%	$78.0141	$78.01	$78.00	$78.00
Purchase #6	$28.91	13.201%	$32.7264	$32.73	$32.75	$32.70
Purchase #7	$14.63	4.375%	$15.2701	$15.27	$15.25	$15.30
7 purchase totals =	$675.41		$756.9717	$756.97	$756.95	$757.00