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	$211.60	3.443%	$218.8854	$218.89	$218.90	$218.90
Purchase #2	$167.40	13.315%	$189.6893	$189.69	$189.70	$189.70
Purchase #3	$79.53	3.106%	$82.0002	$82.00	$82.00	$82.00
Purchase #4	$94.94	5.804%	$100.4503	$100.45	$100.45	$100.50
Purchase #5	$25.32	8.241%	$27.4066	$27.41	$27.40	$27.40
Purchase #6	$237.35	3.708%	$246.1509	$246.15	$246.15	$246.20
Purchase #7	$32.79	13.198%	$37.1176	$37.12	$37.10	$37.10
7 purchase totals =	$848.93		$901.7003	$901.71	$901.70	$901.80