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	$230.26	4.448%	$240.502	$240.50	$240.50	$240.50
Purchase #2	$68.68	9.195%	$74.9951	$75.00	$75.00	$75.00
Purchase #3	$213.96	6.490%	$227.846	$227.85	$227.85	$227.80
Purchase #4	$106.29	5.859%	$112.5175	$112.52	$112.50	$112.50
Purchase #5	$190.28	3.194%	$196.3575	$196.36	$196.35	$196.40
Purchase #6	$196.41	10.765%	$217.5535	$217.55	$217.55	$217.60
Purchase #7	$169.67	9.415%	$185.6444	$185.64	$185.65	$185.60
7 purchase totals =	$1,175.55		$1,255.4160	$1,255.42	$1,255.40	$1,255.40