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	$200.86	8.808%	$218.5517	$218.55	$218.55	$218.60
Purchase #2	$131.83	4.606%	$137.9021	$137.90	$137.90	$137.90
Purchase #3	$90.63	8.517%	$98.349	$98.35	$98.35	$98.30
Purchase #4	$114.84	12.274%	$128.9355	$128.94	$128.95	$128.90
Purchase #5	$72.33	13.685%	$82.2284	$82.23	$82.25	$82.20
Purchase #6	$75.31	3.862%	$78.2185	$78.22	$78.20	$78.20
Purchase #7	$46.27	8.198%	$50.0632	$50.06	$50.05	$50.10
7 purchase totals =	$732.07		$794.2484	$794.25	$794.25	$794.20