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	$74.63	10.602%	$82.5423	$82.54	$82.55	$82.50
Purchase #2	$177.42	6.279%	$188.5602	$188.56	$188.55	$188.60
Purchase #3	$99.73	12.267%	$111.9639	$111.96	$111.95	$112.00
Purchase #4	$111.36	9.402%	$121.8301	$121.83	$121.85	$121.80
Purchase #5	$46.89	8.570%	$50.9085	$50.91	$50.90	$50.90
Purchase #6	$101.31	8.147%	$109.5637	$109.56	$109.55	$109.60
Purchase #7	$66.45	8.457%	$72.0697	$72.07	$72.05	$72.10
7 purchase totals =	$677.79		$737.4384	$737.43	$737.40	$737.50