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	$89.73	10.281%	$98.9551	$98.96	$98.95	$99.00
Purchase #2	$243.63	5.113%	$256.0868	$256.09	$256.10	$256.10
Purchase #3	$121.59	11.826%	$135.9692	$135.97	$135.95	$136.00
Purchase #4	$119.37	12.682%	$134.5085	$134.51	$134.50	$134.50
Purchase #5	$177.79	3.449%	$183.922	$183.92	$183.90	$183.90
Purchase #6	$148.61	5.186%	$156.3169	$156.32	$156.30	$156.30
Purchase #7	$72.25	9.229%	$78.918	$78.92	$78.90	$78.90
7 purchase totals =	$972.97		$1,044.6765	$1,044.69	$1,044.60	$1,044.70