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	$163.97	13.389%	$185.9239	$185.92	$185.90	$185.90
Purchase #2	$171.98	13.121%	$194.5455	$194.55	$194.55	$194.50
Purchase #3	$31.60	7.395%	$33.9368	$33.94	$33.95	$33.90
Purchase #4	$151.43	8.842%	$164.8194	$164.82	$164.80	$164.80
Purchase #5	$68.82	4.569%	$71.9644	$71.96	$71.95	$72.00
Purchase #6	$199.39	4.735%	$208.8311	$208.83	$208.85	$208.80
Purchase #7	$20.48	9.570%	$22.4399	$22.44	$22.45	$22.40
7 purchase totals =	$807.67		$882.4610	$882.46	$882.45	$882.30