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	$192.70	11.861%	$215.5561	$215.56	$215.55	$215.60
Purchase #2	$40.56	4.670%	$42.4542	$42.45	$42.45	$42.50
Purchase #3	$194.29	3.167%	$200.4432	$200.44	$200.45	$200.40
Purchase #4	$145.55	10.107%	$160.2607	$160.26	$160.25	$160.30
Purchase #5	$85.99	6.214%	$91.3334	$91.33	$91.35	$91.30
Purchase #6	$18.87	13.755%	$21.4656	$21.47	$21.45	$21.50
Purchase #7	$35.48	11.530%	$39.5708	$39.57	$39.55	$39.60
7 purchase totals =	$713.44		$771.0840	$771.08	$771.05	$771.20