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	$122.82	11.773%	$137.2796	$137.28	$137.30	$137.30
Purchase #2	$98.54	5.357%	$103.8188	$103.82	$103.80	$103.80
Purchase #3	$248.38	5.849%	$262.9077	$262.91	$262.90	$262.90
Purchase #4	$155.74	6.746%	$166.2462	$166.25	$166.25	$166.20
Purchase #5	$195.86	8.729%	$212.9566	$212.96	$212.95	$213.00
Purchase #6	$192.74	3.816%	$200.095	$200.10	$200.10	$200.10
Purchase #7	$25.63	10.308%	$28.2719	$28.27	$28.25	$28.30
7 purchase totals =	$1,039.71		$1,111.5758	$1,111.59	$1,111.55	$1,111.60