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	$193.80	4.175%	$201.8912	$201.89	$201.90	$201.90
Purchase #2	$166.72	13.872%	$189.8474	$189.85	$189.85	$189.80
Purchase #3	$66.56	9.306%	$72.7541	$72.75	$72.75	$72.80
Purchase #4	$35.35	8.806%	$38.4629	$38.46	$38.45	$38.50
Purchase #5	$155.47	6.700%	$165.8865	$165.89	$165.90	$165.90
Purchase #6	$191.67	4.736%	$200.7475	$200.75	$200.75	$200.70
Purchase #7	$123.69	3.477%	$127.9907	$127.99	$128.00	$128.00
7 purchase totals =	$933.26		$997.5803	$997.58	$997.60	$997.60