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	$104.44	11.533%	$116.4851	$116.49	$116.50	$116.50
Purchase #2	$36.38	11.507%	$40.5662	$40.57	$40.55	$40.60
Purchase #3	$215.73	9.606%	$236.453	$236.45	$236.45	$236.50
Purchase #4	$238.56	4.377%	$249.0018	$249.00	$249.00	$249.00
Purchase #5	$166.33	9.357%	$181.8935	$181.89	$181.90	$181.90
Purchase #6	$122.91	12.818%	$138.6646	$138.66	$138.65	$138.70
Purchase #7	$134.34	9.256%	$146.7745	$146.77	$146.75	$146.80
7 purchase totals =	$1,018.69		$1,109.8387	$1,109.83	$1,109.80	$1,110.00