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	$187.66	12.512%	$211.14	$211.14	$211.15	$211.10
Purchase #2	$83.61	8.496%	$90.7135	$90.71	$90.70	$90.70
Purchase #3	$106.60	6.336%	$113.3542	$113.35	$113.35	$113.40
Purchase #4	$83.82	8.377%	$90.8416	$90.84	$90.85	$90.80
Purchase #5	$13.37	11.725%	$14.9376	$14.94	$14.95	$14.90
Purchase #6	$86.40	5.576%	$91.2177	$91.22	$91.20	$91.20
Purchase #7	$237.89	11.617%	$265.5257	$265.53	$265.55	$265.50
7 purchase totals =	$799.35		$877.7303	$877.73	$877.75	$877.60