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	$56.48	4.863%	$59.2266	$59.23	$59.25	$59.20
Purchase #2	$155.35	7.417%	$166.8723	$166.87	$166.85	$166.90
Purchase #3	$83.36	3.209%	$86.035	$86.04	$86.05	$86.00
Purchase #4	$117.55	6.111%	$124.7335	$124.73	$124.75	$124.70
Purchase #5	$208.77	5.611%	$220.4841	$220.48	$220.50	$220.50
Purchase #6	$51.73	7.403%	$55.5596	$55.56	$55.55	$55.60
Purchase #7	$50.60	11.770%	$56.5556	$56.56	$56.55	$56.60
7 purchase totals =	$723.84		$769.4667	$769.47	$769.50	$769.50