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	$121.90	7.216%	$130.6963	$130.70	$130.70	$130.70
Purchase #2	$165.47	12.313%	$185.8443	$185.84	$185.85	$185.80
Purchase #3	$90.52	13.808%	$103.019	$103.02	$103.00	$103.00
Purchase #4	$47.30	3.132%	$48.7814	$48.78	$48.80	$48.80
Purchase #5	$199.45	11.400%	$222.1873	$222.19	$222.20	$222.20
Purchase #6	$93.90	7.342%	$100.7941	$100.79	$100.80	$100.80
Purchase #7	$250.93	12.318%	$281.8396	$281.84	$281.85	$281.80
7 purchase totals =	$969.47		$1,073.1620	$1,073.16	$1,073.20	$1,073.10