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	$176.86	12.217%	$198.467	$198.47	$198.45	$198.50
Purchase #2	$65.39	11.470%	$72.8902	$72.89	$72.90	$72.90
Purchase #3	$139.76	8.671%	$151.8786	$151.88	$151.90	$151.90
Purchase #4	$158.78	3.617%	$164.5231	$164.52	$164.50	$164.50
Purchase #5	$129.66	10.665%	$143.4882	$143.49	$143.50	$143.50
Purchase #6	$73.94	10.708%	$81.8575	$81.86	$81.85	$81.90
Purchase #7	$179.70	7.251%	$192.73	$192.73	$192.75	$192.70
7 purchase totals =	$924.09		$1,005.8346	$1,005.84	$1,005.85	$1,005.90