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	$213.79	6.384%	$227.4384	$227.44	$227.45	$227.40
Purchase #2	$83.81	6.254%	$89.0515	$89.05	$89.05	$89.10
Purchase #3	$99.60	12.221%	$111.7721	$111.77	$111.75	$111.80
Purchase #4	$145.42	13.695%	$165.3353	$165.34	$165.35	$165.30
Purchase #5	$245.35	7.480%	$263.7022	$263.70	$263.70	$263.70
Purchase #6	$183.43	7.313%	$196.8442	$196.84	$196.85	$196.80
Purchase #7	$228.36	11.645%	$254.9525	$254.95	$254.95	$255.00
7 purchase totals =	$1,199.76		$1,309.0962	$1,309.09	$1,309.10	$1,309.10