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	$247.39	6.620%	$263.7672	$263.77	$263.75	$263.80
Purchase #2	$40.87	11.236%	$45.4622	$45.46	$45.45	$45.50
Purchase #3	$47.54	10.386%	$52.4775	$52.48	$52.50	$52.50
Purchase #4	$213.42	6.514%	$227.3222	$227.32	$227.30	$227.30
Purchase #5	$81.30	9.327%	$88.8829	$88.88	$88.90	$88.90
Purchase #6	$216.83	13.846%	$246.8523	$246.85	$246.85	$246.90
Purchase #7	$113.41	9.167%	$123.8063	$123.81	$123.80	$123.80
7 purchase totals =	$960.76		$1,048.5706	$1,048.57	$1,048.55	$1,048.70