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	$35.56	6.333%	$37.812	$37.81	$37.80	$37.80
Purchase #2	$32.53	11.274%	$36.1974	$36.20	$36.20	$36.20
Purchase #3	$250.62	9.789%	$275.1532	$275.15	$275.15	$275.20
Purchase #4	$236.71	9.219%	$258.5323	$258.53	$258.55	$258.50
Purchase #5	$203.58	10.699%	$225.361	$225.36	$225.35	$225.40
Purchase #6	$82.25	12.295%	$92.3626	$92.36	$92.35	$92.40
Purchase #7	$101.28	4.345%	$105.6806	$105.68	$105.70	$105.70
7 purchase totals =	$942.53		$1,031.0991	$1,031.09	$1,031.10	$1,031.20