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	$236.72	12.308%	$265.8555	$265.86	$265.85	$265.90
Purchase #2	$17.83	9.272%	$19.4832	$19.48	$19.50	$19.50
Purchase #3	$202.61	6.361%	$215.498	$215.50	$215.50	$215.50
Purchase #4	$93.29	13.812%	$106.1752	$106.18	$106.20	$106.20
Purchase #5	$18.74	7.147%	$20.0793	$20.08	$20.10	$20.10
Purchase #6	$133.26	13.757%	$151.5926	$151.59	$151.60	$151.60
Purchase #7	$59.96	9.343%	$65.5621	$65.56	$65.55	$65.60
7 purchase totals =	$762.41		$844.2459	$844.25	$844.30	$844.40