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	$104.74	7.403%	$112.4939	$112.49	$112.50	$112.50
Purchase #2	$134.55	13.660%	$152.9295	$152.93	$152.95	$152.90
Purchase #3	$189.73	9.686%	$208.1072	$208.11	$208.10	$208.10
Purchase #4	$125.50	8.829%	$136.5804	$136.58	$136.60	$136.60
Purchase #5	$201.67	5.114%	$211.9834	$211.98	$212.00	$212.00
Purchase #6	$123.67	6.601%	$131.8335	$131.83	$131.85	$131.80
Purchase #7	$66.37	9.275%	$72.5258	$72.53	$72.55	$72.50
7 purchase totals =	$946.23		$1,026.4537	$1,026.45	$1,026.55	$1,026.40