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	$192.26	10.798%	$213.0202	$213.02	$213.00	$213.00
Purchase #2	$160.70	4.868%	$168.5229	$168.52	$168.50	$168.50
Purchase #3	$193.99	7.515%	$208.5683	$208.57	$208.55	$208.60
Purchase #4	$100.69	12.597%	$113.3739	$113.37	$113.35	$113.40
Purchase #5	$56.70	3.794%	$58.8512	$58.85	$58.85	$58.90
Purchase #6	$219.34	11.874%	$245.3844	$245.38	$245.40	$245.40
Purchase #7	$52.84	12.524%	$59.4577	$59.46	$59.45	$59.50
7 purchase totals =	$976.52		$1,067.1786	$1,067.17	$1,067.10	$1,067.30