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	$41.67	9.686%	$45.7062	$45.71	$45.70	$45.70
Purchase #2	$123.43	6.139%	$131.0074	$131.01	$131.00	$131.00
Purchase #3	$161.38	8.708%	$175.433	$175.43	$175.45	$175.40
Purchase #4	$42.67	9.762%	$46.8354	$46.84	$46.85	$46.80
Purchase #5	$169.90	13.204%	$192.3336	$192.33	$192.35	$192.30
Purchase #6	$250.69	13.576%	$284.7237	$284.72	$284.70	$284.70
Purchase #7	$213.60	12.714%	$240.7571	$240.76	$240.75	$240.80
7 purchase totals =	$1,003.34		$1,116.7964	$1,116.80	$1,116.80	$1,116.70