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	$42.85	8.128%	$46.3328	$46.33	$46.35	$46.30
Purchase #2	$232.40	11.418%	$258.9354	$258.94	$258.95	$258.90
Purchase #3	$179.25	13.400%	$203.2695	$203.27	$203.25	$203.30
Purchase #4	$59.62	3.785%	$61.8766	$61.88	$61.90	$61.90
Purchase #5	$182.52	7.633%	$196.4518	$196.45	$196.45	$196.50
Purchase #6	$30.90	3.176%	$31.8814	$31.88	$31.90	$31.90
Purchase #7	$92.35	9.406%	$101.0364	$101.04	$101.05	$101.00
7 purchase totals =	$819.89		$899.7839	$899.79	$899.85	$899.80