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	$228.52	7.350%	$245.3162	$245.32	$245.30	$245.30
Purchase #2	$78.46	3.215%	$80.9825	$80.98	$81.00	$81.00
Purchase #3	$53.41	6.334%	$56.793	$56.79	$56.80	$56.80
Purchase #4	$136.81	10.812%	$151.6019	$151.60	$151.60	$151.60
Purchase #5	$134.83	11.628%	$150.508	$150.51	$150.50	$150.50
Purchase #6	$245.33	8.714%	$266.7081	$266.71	$266.70	$266.70
Purchase #7	$246.93	13.131%	$279.3544	$279.35	$279.35	$279.40
7 purchase totals =	$1,124.29		$1,231.2641	$1,231.26	$1,231.25	$1,231.30