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	$119.89	3.380%	$123.9423	$123.94	$123.95	$123.90
Purchase #2	$134.78	5.714%	$142.4813	$142.48	$142.50	$142.50
Purchase #3	$31.49	12.418%	$35.4004	$35.40	$35.40	$35.40
Purchase #4	$14.32	7.234%	$15.3559	$15.36	$15.35	$15.40
Purchase #5	$92.89	7.113%	$99.4973	$99.50	$99.50	$99.50
Purchase #6	$89.72	3.571%	$92.9239	$92.92	$92.90	$92.90
Purchase #7	$201.51	4.364%	$210.3039	$210.30	$210.30	$210.30
7 purchase totals =	$684.60		$719.9050	$719.90	$719.90	$719.90