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	$235.32	11.732%	$262.9277	$262.93	$262.95	$262.90
Purchase #2	$104.93	6.353%	$111.5962	$111.60	$111.60	$111.60
Purchase #3	$88.69	12.477%	$99.7559	$99.76	$99.75	$99.80
Purchase #4	$137.44	13.849%	$156.4741	$156.47	$156.45	$156.50
Purchase #5	$211.59	8.310%	$229.1731	$229.17	$229.15	$229.20
Purchase #6	$227.44	4.808%	$238.3753	$238.38	$238.40	$238.40
Purchase #7	$232.30	4.401%	$242.5235	$242.52	$242.50	$242.50
7 purchase totals =	$1,237.71		$1,340.8258	$1,340.83	$1,340.80	$1,340.90