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	$167.31	7.197%	$179.3513	$179.35	$179.35	$179.40
Purchase #2	$84.51	3.434%	$87.4121	$87.41	$87.40	$87.40
Purchase #3	$83.66	8.313%	$90.6147	$90.61	$90.60	$90.60
Purchase #4	$93.27	5.541%	$98.4381	$98.44	$98.45	$98.40
Purchase #5	$232.37	11.192%	$258.3769	$258.38	$258.40	$258.40
Purchase #6	$127.60	3.217%	$131.7049	$131.70	$131.70	$131.70
Purchase #7	$250.40	3.322%	$258.7183	$258.72	$258.70	$258.70
7 purchase totals =	$1,039.12		$1,104.6163	$1,104.61	$1,104.60	$1,104.60