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	$93.77	7.265%	$100.5824	$100.58	$100.60	$100.60
Purchase #2	$84.25	11.872%	$94.2522	$94.25	$94.25	$94.30
Purchase #3	$186.27	10.468%	$205.7687	$205.77	$205.75	$205.80
Purchase #4	$245.39	10.812%	$271.9216	$271.92	$271.90	$271.90
Purchase #5	$89.43	3.574%	$92.6262	$92.63	$92.65	$92.60
Purchase #6	$14.56	5.275%	$15.328	$15.33	$15.35	$15.30
Purchase #7	$149.87	11.277%	$166.7708	$166.77	$166.75	$166.80
7 purchase totals =	$863.54		$947.2499	$947.25	$947.25	$947.30