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	$139.61	3.864%	$145.0045	$145.00	$145.00	$145.00
Purchase #2	$25.98	7.156%	$27.8391	$27.84	$27.85	$27.80
Purchase #3	$201.32	8.114%	$217.6551	$217.66	$217.65	$217.70
Purchase #4	$61.43	6.811%	$65.614	$65.61	$65.60	$65.60
Purchase #5	$182.59	9.274%	$199.5234	$199.52	$199.50	$199.50
Purchase #6	$69.50	4.360%	$72.5302	$72.53	$72.55	$72.50
Purchase #7	$31.71	6.301%	$33.708	$33.71	$33.70	$33.70
7 purchase totals =	$712.14		$761.8743	$761.87	$761.85	$761.80