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	$70.33	13.117%	$79.5552	$79.56	$79.55	$79.60
Purchase #2	$34.29	6.520%	$36.5257	$36.53	$36.55	$36.50
Purchase #3	$35.69	12.559%	$40.1723	$40.17	$40.15	$40.20
Purchase #4	$246.51	12.182%	$276.5398	$276.54	$276.55	$276.50
Purchase #5	$63.27	13.433%	$71.7691	$71.77	$71.75	$71.80
Purchase #6	$86.86	4.607%	$90.8616	$90.86	$90.85	$90.90
Purchase #7	$150.29	10.799%	$166.5198	$166.52	$166.50	$166.50
7 purchase totals =	$687.24		$761.9435	$761.95	$761.90	$762.00