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	$211.56	9.337%	$231.3134	$231.31	$231.30	$231.30
Purchase #2	$182.62	4.162%	$190.2206	$190.22	$190.20	$190.20
Purchase #3	$99.48	8.618%	$108.0532	$108.05	$108.05	$108.10
Purchase #4	$250.65	4.337%	$261.5207	$261.52	$261.50	$261.50
Purchase #5	$214.58	3.431%	$221.9422	$221.94	$221.95	$221.90
Purchase #6	$99.79	5.565%	$105.3433	$105.34	$105.35	$105.30
Purchase #7	$29.32	8.800%	$31.9002	$31.90	$31.90	$31.90
7 purchase totals =	$1,088.00		$1,150.2936	$1,150.28	$1,150.25	$1,150.20