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	$161.97	5.714%	$171.225	$171.23	$171.25	$171.20
Purchase #2	$89.66	7.265%	$96.1738	$96.17	$96.15	$96.20
Purchase #3	$100.94	8.764%	$109.7864	$109.79	$109.80	$109.80
Purchase #4	$200.65	7.855%	$216.4111	$216.41	$216.40	$216.40
Purchase #5	$42.89	5.141%	$45.095	$45.10	$45.10	$45.10
Purchase #6	$93.61	10.545%	$103.4812	$103.48	$103.50	$103.50
Purchase #7	$140.60	13.678%	$159.8313	$159.83	$159.85	$159.80
7 purchase totals =	$830.32		$902.0038	$902.01	$902.05	$902.00