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	$145.71	11.596%	$162.6065	$162.61	$162.60	$162.60
Purchase #2	$209.87	11.778%	$234.5885	$234.59	$234.60	$234.60
Purchase #3	$57.65	5.593%	$60.8744	$60.87	$60.85	$60.90
Purchase #4	$143.49	7.384%	$154.0853	$154.09	$154.10	$154.10
Purchase #5	$169.86	9.220%	$185.5211	$185.52	$185.50	$185.50
Purchase #6	$41.58	13.589%	$47.2303	$47.23	$47.25	$47.20
Purchase #7	$80.48	11.567%	$89.7891	$89.79	$89.80	$89.80
7 purchase totals =	$848.64		$934.6952	$934.70	$934.70	$934.70