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	$174.47	13.375%	$197.8054	$197.81	$197.80	$197.80
Purchase #2	$80.43	3.601%	$83.3263	$83.33	$83.35	$83.30
Purchase #3	$138.84	5.752%	$146.8261	$146.83	$146.85	$146.80
Purchase #4	$192.90	9.701%	$211.6132	$211.61	$211.60	$211.60
Purchase #5	$156.37	10.164%	$172.2634	$172.26	$172.25	$172.30
Purchase #6	$93.46	4.283%	$97.4629	$97.46	$97.45	$97.50
Purchase #7	$230.33	3.560%	$238.5297	$238.53	$238.55	$238.50
7 purchase totals =	$1,066.80		$1,147.8270	$1,147.83	$1,147.85	$1,147.80