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	$117.81	11.372%	$131.2074	$131.21	$131.20	$131.20
Purchase #2	$101.96	13.378%	$115.6002	$115.60	$115.60	$115.60
Purchase #3	$156.61	6.520%	$166.821	$166.82	$166.80	$166.80
Purchase #4	$188.39	10.859%	$208.8473	$208.85	$208.85	$208.80
Purchase #5	$92.32	8.359%	$100.037	$100.04	$100.05	$100.00
Purchase #6	$250.27	3.701%	$259.5325	$259.53	$259.55	$259.50
Purchase #7	$85.83	10.588%	$94.9177	$94.92	$94.90	$94.90
7 purchase totals =	$993.19		$1,076.9631	$1,076.97	$1,076.95	$1,076.80