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	$107.67	11.121%	$119.644	$119.64	$119.65	$119.60
Purchase #2	$86.67	8.318%	$93.8792	$93.88	$93.90	$93.90
Purchase #3	$166.59	7.549%	$179.1659	$179.17	$179.15	$179.20
Purchase #4	$131.44	7.752%	$141.6292	$141.63	$141.65	$141.60
Purchase #5	$96.90	3.808%	$100.59	$100.59	$100.60	$100.60
Purchase #6	$153.59	5.645%	$162.2602	$162.26	$162.25	$162.30
Purchase #7	$200.72	3.678%	$208.1025	$208.10	$208.10	$208.10
7 purchase totals =	$943.58		$1,005.2710	$1,005.27	$1,005.30	$1,005.30