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	$217.60	8.732%	$236.6008	$236.60	$236.60	$236.60
Purchase #2	$80.37	7.388%	$86.3077	$86.31	$86.30	$86.30
Purchase #3	$120.44	10.280%	$132.8212	$132.82	$132.80	$132.80
Purchase #4	$141.81	10.507%	$156.71	$156.71	$156.70	$156.70
Purchase #5	$139.50	9.789%	$153.1557	$153.16	$153.15	$153.20
Purchase #6	$224.73	7.814%	$242.2904	$242.29	$242.30	$242.30
Purchase #7	$132.48	11.634%	$147.8927	$147.89	$147.90	$147.90
7 purchase totals =	$1,056.93		$1,155.7785	$1,155.78	$1,155.75	$1,155.80