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	$55.80	7.236%	$59.8377	$59.84	$59.85	$59.80
Purchase #2	$148.59	4.238%	$154.8872	$154.89	$154.90	$154.90
Purchase #3	$227.91	11.704%	$254.5846	$254.58	$254.60	$254.60
Purchase #4	$78.94	5.772%	$83.4964	$83.50	$83.50	$83.50
Purchase #5	$168.73	3.673%	$174.9275	$174.93	$174.95	$174.90
Purchase #6	$97.31	3.600%	$100.8132	$100.81	$100.80	$100.80
Purchase #7	$183.36	8.823%	$199.5379	$199.54	$199.55	$199.50
7 purchase totals =	$960.64		$1,028.0845	$1,028.09	$1,028.15	$1,028.00