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	$192.81	13.493%	$218.8259	$218.83	$218.85	$218.80
Purchase #2	$69.45	7.774%	$74.849	$74.85	$74.85	$74.80
Purchase #3	$50.31	9.128%	$54.9023	$54.90	$54.90	$54.90
Purchase #4	$89.30	3.197%	$92.1549	$92.15	$92.15	$92.20
Purchase #5	$203.80	5.862%	$215.7468	$215.75	$215.75	$215.70
Purchase #6	$102.66	9.112%	$112.0144	$112.01	$112.00	$112.00
Purchase #7	$160.89	7.470%	$172.9085	$172.91	$172.90	$172.90
7 purchase totals =	$869.22		$941.4018	$941.40	$941.40	$941.30