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	$151.44	13.256%	$171.5149	$171.51	$171.50	$171.50
Purchase #2	$72.77	6.573%	$77.5532	$77.55	$77.55	$77.60
Purchase #3	$66.42	10.443%	$73.3562	$73.36	$73.35	$73.40
Purchase #4	$202.38	10.530%	$223.6906	$223.69	$223.70	$223.70
Purchase #5	$42.82	6.850%	$45.7532	$45.75	$45.75	$45.80
Purchase #6	$216.31	4.506%	$226.0569	$226.06	$226.05	$226.10
Purchase #7	$82.93	6.167%	$88.0443	$88.04	$88.05	$88.00
7 purchase totals =	$835.07		$905.9693	$905.96	$905.95	$906.10