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	$35.84	5.561%	$37.8331	$37.83	$37.85	$37.80
Purchase #2	$180.67	9.616%	$198.0432	$198.04	$198.05	$198.00
Purchase #3	$100.83	4.524%	$105.3915	$105.39	$105.40	$105.40
Purchase #4	$243.28	4.600%	$254.4709	$254.47	$254.45	$254.50
Purchase #5	$243.29	8.323%	$263.539	$263.54	$263.55	$263.50
Purchase #6	$216.80	12.338%	$243.5488	$243.55	$243.55	$243.50
Purchase #7	$217.60	10.728%	$240.9441	$240.94	$240.95	$240.90
7 purchase totals =	$1,238.31		$1,343.7706	$1,343.76	$1,343.80	$1,343.60