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	$216.30	10.180%	$238.3193	$238.32	$238.30	$238.30
Purchase #2	$17.67	4.446%	$18.4556	$18.46	$18.45	$18.50
Purchase #3	$7.85	6.630%	$8.3705	$8.37	$8.35	$8.40
Purchase #4	$131.65	9.682%	$144.3964	$144.40	$144.40	$144.40
Purchase #5	$156.89	9.296%	$171.4745	$171.47	$171.45	$171.50
Purchase #6	$100.43	12.799%	$113.284	$113.28	$113.30	$113.30
Purchase #7	$244.97	10.684%	$271.1426	$271.14	$271.15	$271.10
7 purchase totals =	$875.76		$965.4429	$965.44	$965.40	$965.50