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	$103.71	9.488%	$113.55	$113.55	$113.55	$113.60
Purchase #2	$241.35	12.649%	$271.8784	$271.88	$271.90	$271.90
Purchase #3	$136.70	4.240%	$142.4961	$142.50	$142.50	$142.50
Purchase #4	$98.61	12.388%	$110.8258	$110.83	$110.85	$110.80
Purchase #5	$211.85	7.377%	$227.4782	$227.48	$227.50	$227.50
Purchase #6	$92.37	8.853%	$100.5475	$100.55	$100.55	$100.50
Purchase #7	$178.90	13.498%	$203.0479	$203.05	$203.05	$203.00
7 purchase totals =	$1,063.49		$1,169.8239	$1,169.84	$1,169.90	$1,169.80