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	$90.90	6.509%	$96.8167	$96.82	$96.80	$96.80
Purchase #2	$78.89	12.872%	$89.0447	$89.04	$89.05	$89.00
Purchase #3	$228.68	9.272%	$249.8832	$249.88	$249.90	$249.90
Purchase #4	$224.68	8.315%	$243.3621	$243.36	$243.35	$243.40
Purchase #5	$107.57	3.739%	$111.592	$111.59	$111.60	$111.60
Purchase #6	$66.39	9.332%	$72.5855	$72.59	$72.60	$72.60
Purchase #7	$153.65	7.165%	$164.659	$164.66	$164.65	$164.70
7 purchase totals =	$950.76		$1,027.9432	$1,027.94	$1,027.95	$1,028.00