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	$101.44	10.261%	$111.8488	$111.85	$111.85	$111.80
Purchase #2	$168.81	5.500%	$178.0946	$178.09	$178.10	$178.10
Purchase #3	$90.41	11.626%	$100.9211	$100.92	$100.90	$100.90
Purchase #4	$22.78	9.783%	$25.0086	$25.01	$25.00	$25.00
Purchase #5	$79.43	6.403%	$84.5159	$84.52	$84.50	$84.50
Purchase #6	$170.39	9.704%	$186.9246	$186.92	$186.90	$186.90
Purchase #7	$91.59	13.550%	$104.0004	$104.00	$104.00	$104.00
7 purchase totals =	$724.85		$791.3140	$791.31	$791.25	$791.20