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	$38.33	7.151%	$41.071	$41.07	$41.05	$41.10
Purchase #2	$77.25	10.382%	$85.2701	$85.27	$85.25	$85.30
Purchase #3	$169.95	7.105%	$182.0249	$182.02	$182.00	$182.00
Purchase #4	$64.80	3.645%	$67.162	$67.16	$67.15	$67.20
Purchase #5	$59.35	8.537%	$64.4167	$64.42	$64.40	$64.40
Purchase #6	$169.67	11.741%	$189.591	$189.59	$189.60	$189.60
Purchase #7	$189.31	12.851%	$213.6382	$213.64	$213.65	$213.60
7 purchase totals =	$768.66		$843.1739	$843.17	$843.10	$843.20