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	$94.26	13.138%	$106.6439	$106.64	$106.65	$106.60
Purchase #2	$6.47	13.586%	$7.349	$7.35	$7.35	$7.30
Purchase #3	$214.71	13.330%	$243.3308	$243.33	$243.35	$243.30
Purchase #4	$19.68	4.158%	$20.4983	$20.50	$20.50	$20.50
Purchase #5	$77.38	10.136%	$85.2232	$85.22	$85.20	$85.20
Purchase #6	$40.31	6.313%	$42.8548	$42.85	$42.85	$42.90
Purchase #7	$161.63	4.151%	$168.3393	$168.34	$168.35	$168.30
7 purchase totals =	$614.44		$674.2393	$674.23	$674.25	$674.10