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	$249.72	5.692%	$263.9341	$263.93	$263.95	$263.90
Purchase #2	$33.70	4.287%	$35.1447	$35.14	$35.15	$35.10
Purchase #3	$151.58	8.802%	$164.9221	$164.92	$164.90	$164.90
Purchase #4	$76.48	13.567%	$86.856	$86.86	$86.85	$86.90
Purchase #5	$201.33	4.764%	$210.9214	$210.92	$210.90	$210.90
Purchase #6	$183.27	3.867%	$190.3571	$190.36	$190.35	$190.40
Purchase #7	$29.68	4.470%	$31.0067	$31.01	$31.00	$31.00
7 purchase totals =	$925.76		$983.1421	$983.14	$983.10	$983.10