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	$170.51	13.167%	$192.9611	$192.96	$192.95	$193.00
Purchase #2	$226.53	10.741%	$250.8616	$250.86	$250.85	$250.90
Purchase #3	$223.43	4.181%	$232.7716	$232.77	$232.75	$232.80
Purchase #4	$158.82	4.841%	$166.5085	$166.51	$166.50	$166.50
Purchase #5	$85.37	5.586%	$90.1388	$90.14	$90.15	$90.10
Purchase #6	$109.57	3.396%	$113.291	$113.29	$113.30	$113.30
Purchase #7	$126.59	9.255%	$138.3059	$138.31	$138.30	$138.30
7 purchase totals =	$1,100.82		$1,184.8385	$1,184.84	$1,184.80	$1,184.90