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	$126.94	8.646%	$137.9152	$137.92	$137.90	$137.90
Purchase #2	$206.63	11.619%	$230.6383	$230.64	$230.65	$230.60
Purchase #3	$67.67	6.732%	$72.2255	$72.23	$72.25	$72.20
Purchase #4	$170.78	11.398%	$190.2455	$190.25	$190.25	$190.20
Purchase #5	$178.93	4.681%	$187.3057	$187.31	$187.30	$187.30
Purchase #6	$137.72	4.483%	$143.894	$143.89	$143.90	$143.90
Purchase #7	$109.30	12.120%	$122.5472	$122.55	$122.55	$122.50
7 purchase totals =	$997.97		$1,084.7714	$1,084.79	$1,084.80	$1,084.60