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	$97.82	7.337%	$104.9971	$105.00	$105.00	$105.00
Purchase #2	$148.44	8.380%	$160.8793	$160.88	$160.90	$160.90
Purchase #3	$38.58	12.380%	$43.3562	$43.36	$43.35	$43.40
Purchase #4	$173.94	7.409%	$186.8272	$186.83	$186.85	$186.80
Purchase #5	$210.98	13.168%	$238.7618	$238.76	$238.75	$238.80
Purchase #6	$235.33	13.141%	$266.2547	$266.25	$266.25	$266.30
Purchase #7	$84.32	6.443%	$89.7527	$89.75	$89.75	$89.80
7 purchase totals =	$989.41		$1,090.8290	$1,090.83	$1,090.85	$1,091.00