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	$143.67	9.184%	$156.8647	$156.86	$156.85	$156.90
Purchase #2	$175.90	10.419%	$194.227	$194.23	$194.25	$194.20
Purchase #3	$38.97	12.430%	$43.814	$43.81	$43.80	$43.80
Purchase #4	$168.35	8.387%	$182.4695	$182.47	$182.45	$182.50
Purchase #5	$102.31	7.661%	$110.148	$110.15	$110.15	$110.10
Purchase #6	$89.74	5.113%	$94.3284	$94.33	$94.35	$94.30
Purchase #7	$105.58	7.649%	$113.6558	$113.66	$113.65	$113.70
7 purchase totals =	$824.52		$895.5074	$895.51	$895.50	$895.50