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	$10.31	5.148%	$10.8408	$10.84	$10.85	$10.80
Purchase #2	$148.57	13.706%	$168.933	$168.93	$168.95	$168.90
Purchase #3	$129.80	13.255%	$147.005	$147.01	$147.00	$147.00
Purchase #4	$218.73	6.274%	$232.4531	$232.45	$232.45	$232.50
Purchase #5	$151.98	3.697%	$157.5987	$157.60	$157.60	$157.60
Purchase #6	$124.27	4.802%	$130.2374	$130.24	$130.25	$130.20
Purchase #7	$153.83	10.209%	$169.5345	$169.53	$169.55	$169.50
7 purchase totals =	$937.49		$1,016.6025	$1,016.60	$1,016.65	$1,016.50