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	$220.54	11.611%	$246.1469	$246.15	$246.15	$246.10
Purchase #2	$179.64	4.314%	$187.3897	$187.39	$187.40	$187.40
Purchase #3	$150.29	11.862%	$168.1174	$168.12	$168.10	$168.10
Purchase #4	$39.44	10.497%	$43.58	$43.58	$43.60	$43.60
Purchase #5	$72.47	8.430%	$78.5792	$78.58	$78.60	$78.60
Purchase #6	$232.57	3.249%	$240.1262	$240.13	$240.15	$240.10
Purchase #7	$188.29	12.204%	$211.2689	$211.27	$211.25	$211.30
7 purchase totals =	$1,083.24		$1,175.2083	$1,175.22	$1,175.25	$1,175.20