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	$123.89	7.808%	$133.5633	$133.56	$133.55	$133.60
Purchase #2	$151.31	11.372%	$168.517	$168.52	$168.50	$168.50
Purchase #3	$18.58	12.814%	$20.9608	$20.96	$20.95	$21.00
Purchase #4	$66.87	12.383%	$75.1505	$75.15	$75.15	$75.20
Purchase #5	$38.83	11.211%	$43.1832	$43.18	$43.20	$43.20
Purchase #6	$72.47	5.475%	$76.4377	$76.44	$76.45	$76.40
Purchase #7	$202.98	3.684%	$210.4578	$210.46	$210.45	$210.50
7 purchase totals =	$674.93		$728.2703	$728.27	$728.25	$728.40