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	$117.52	12.290%	$131.9632	$131.96	$131.95	$132.00
Purchase #2	$102.78	10.222%	$113.2862	$113.29	$113.30	$113.30
Purchase #3	$186.89	8.741%	$203.2261	$203.23	$203.25	$203.20
Purchase #4	$44.35	13.109%	$50.1638	$50.16	$50.15	$50.20
Purchase #5	$82.54	4.242%	$86.0413	$86.04	$86.05	$86.00
Purchase #6	$23.94	3.387%	$24.7508	$24.75	$24.75	$24.80
Purchase #7	$181.42	4.667%	$189.8869	$189.89	$189.90	$189.90
7 purchase totals =	$739.44		$799.3183	$799.32	$799.35	$799.40