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	$201.77	13.186%	$228.3754	$228.38	$228.40	$228.40
Purchase #2	$6.66	13.533%	$7.5613	$7.56	$7.55	$7.60
Purchase #3	$240.31	7.199%	$257.6099	$257.61	$257.60	$257.60
Purchase #4	$40.96	11.709%	$45.756	$45.76	$45.75	$45.80
Purchase #5	$215.99	7.566%	$232.3318	$232.33	$232.35	$232.30
Purchase #6	$81.80	10.688%	$90.5428	$90.54	$90.55	$90.50
Purchase #7	$133.50	5.205%	$140.4487	$140.45	$140.45	$140.40
7 purchase totals =	$920.99		$1,002.6259	$1,002.63	$1,002.65	$1,002.60