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	$169.27	13.777%	$192.5903	$192.59	$192.60	$192.60
Purchase #2	$137.31	10.851%	$152.2095	$152.21	$152.20	$152.20
Purchase #3	$87.95	12.181%	$98.6632	$98.66	$98.65	$98.70
Purchase #4	$57.57	10.238%	$63.464	$63.46	$63.45	$63.50
Purchase #5	$208.39	6.583%	$222.1083	$222.11	$222.10	$222.10
Purchase #6	$120.84	5.299%	$127.2433	$127.24	$127.25	$127.20
Purchase #7	$21.90	7.592%	$23.5626	$23.56	$23.55	$23.60
7 purchase totals =	$803.23		$879.8412	$879.83	$879.80	$879.90