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	$197.41	9.574%	$216.31	$216.31	$216.30	$216.30
Purchase #2	$85.80	13.666%	$97.5254	$97.53	$97.55	$97.50
Purchase #3	$48.70	9.310%	$53.234	$53.23	$53.25	$53.20
Purchase #4	$209.49	4.337%	$218.5756	$218.58	$218.60	$218.60
Purchase #5	$131.55	4.414%	$137.3566	$137.36	$137.35	$137.40
Purchase #6	$158.92	8.569%	$172.5379	$172.54	$172.55	$172.50
Purchase #7	$100.84	12.776%	$113.7233	$113.72	$113.70	$113.70
7 purchase totals =	$932.71		$1,009.2628	$1,009.27	$1,009.30	$1,009.20