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	$126.75	11.287%	$141.0563	$141.06	$141.05	$141.10
Purchase #2	$68.65	7.574%	$73.8496	$73.85	$73.85	$73.80
Purchase #3	$238.85	6.166%	$253.5775	$253.58	$253.60	$253.60
Purchase #4	$76.83	11.291%	$85.5049	$85.50	$85.50	$85.50
Purchase #5	$205.71	8.417%	$223.0246	$223.02	$223.00	$223.00
Purchase #6	$45.85	10.211%	$50.5317	$50.53	$50.55	$50.50
Purchase #7	$70.79	3.319%	$73.1395	$73.14	$73.15	$73.10
7 purchase totals =	$833.43		$900.6841	$900.68	$900.70	$900.60