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	$197.42	9.719%	$216.6072	$216.61	$216.60	$216.60
Purchase #2	$187.59	13.485%	$212.8865	$212.89	$212.90	$212.90
Purchase #3	$35.51	8.504%	$38.5298	$38.53	$38.55	$38.50
Purchase #4	$172.39	11.851%	$192.8199	$192.82	$192.80	$192.80
Purchase #5	$117.48	8.867%	$127.897	$127.90	$127.90	$127.90
Purchase #6	$153.94	11.113%	$171.0474	$171.05	$171.05	$171.00
Purchase #7	$156.43	9.659%	$171.5396	$171.54	$171.55	$171.50
7 purchase totals =	$1,020.76		$1,131.3274	$1,131.34	$1,131.35	$1,131.20