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	$83.95	11.385%	$93.5077	$93.51	$93.50	$93.50
Purchase #2	$81.81	11.566%	$91.2721	$91.27	$91.25	$91.30
Purchase #3	$102.66	8.706%	$111.5976	$111.60	$111.60	$111.60
Purchase #4	$169.89	12.482%	$191.0957	$191.10	$191.10	$191.10
Purchase #5	$152.85	8.357%	$165.6237	$165.62	$165.60	$165.60
Purchase #6	$99.60	9.487%	$109.0491	$109.05	$109.05	$109.00
Purchase #7	$111.84	7.841%	$120.6094	$120.61	$120.60	$120.60
7 purchase totals =	$802.60		$882.7553	$882.76	$882.70	$882.70