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	$180.64	5.299%	$190.2121	$190.21	$190.20	$190.20
Purchase #2	$178.74	10.106%	$196.8035	$196.80	$196.80	$196.80
Purchase #3	$207.53	3.764%	$215.3414	$215.34	$215.35	$215.30
Purchase #4	$54.91	10.587%	$60.7233	$60.72	$60.70	$60.70
Purchase #5	$201.37	9.584%	$220.6693	$220.67	$220.65	$220.70
Purchase #6	$90.27	13.643%	$102.5855	$102.59	$102.60	$102.60
Purchase #7	$43.95	3.278%	$45.3907	$45.39	$45.40	$45.40
7 purchase totals =	$957.41		$1,031.7258	$1,031.72	$1,031.70	$1,031.70