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	$232.60	11.204%	$258.6605	$258.66	$258.65	$258.70
Purchase #2	$234.29	3.293%	$242.0052	$242.01	$242.00	$242.00
Purchase #3	$69.32	13.245%	$78.5014	$78.50	$78.50	$78.50
Purchase #4	$244.94	10.427%	$270.4799	$270.48	$270.50	$270.50
Purchase #5	$229.27	5.764%	$242.4851	$242.49	$242.50	$242.50
Purchase #6	$247.70	6.142%	$262.9137	$262.91	$262.90	$262.90
Purchase #7	$73.36	10.309%	$80.9227	$80.92	$80.90	$80.90
7 purchase totals =	$1,331.48		$1,435.9685	$1,435.97	$1,435.95	$1,436.00