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	$79.44	8.861%	$86.4792	$86.48	$86.50	$86.50
Purchase #2	$77.94	7.708%	$83.9476	$83.95	$83.95	$83.90
Purchase #3	$175.38	13.315%	$198.7318	$198.73	$198.75	$198.70
Purchase #4	$101.97	9.322%	$111.4756	$111.48	$111.50	$111.50
Purchase #5	$149.67	4.690%	$156.6895	$156.69	$156.70	$156.70
Purchase #6	$86.61	6.102%	$91.8949	$91.89	$91.90	$91.90
Purchase #7	$152.82	13.519%	$173.4797	$173.48	$173.50	$173.50
7 purchase totals =	$823.83		$902.6983	$902.70	$902.80	$902.70