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	$164.86	12.713%	$185.8187	$185.82	$185.80	$185.80
Purchase #2	$19.76	7.808%	$21.3029	$21.30	$21.30	$21.30
Purchase #3	$140.60	3.798%	$145.94	$145.94	$145.95	$145.90
Purchase #4	$58.30	4.587%	$60.9742	$60.97	$60.95	$61.00
Purchase #5	$101.57	8.219%	$109.918	$109.92	$109.90	$109.90
Purchase #6	$210.43	5.601%	$222.2162	$222.22	$222.20	$222.20
Purchase #7	$55.68	7.357%	$59.7764	$59.78	$59.80	$59.80
7 purchase totals =	$751.20		$805.9464	$805.95	$805.90	$805.90