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	$188.64	6.464%	$200.8337	$200.83	$200.85	$200.80
Purchase #2	$246.78	6.400%	$262.5739	$262.57	$262.55	$262.60
Purchase #3	$145.73	3.783%	$151.243	$151.24	$151.25	$151.20
Purchase #4	$215.54	7.226%	$231.1149	$231.11	$231.10	$231.10
Purchase #5	$184.32	11.708%	$205.9002	$205.90	$205.90	$205.90
Purchase #6	$132.36	11.434%	$147.494	$147.49	$147.50	$147.50
Purchase #7	$151.60	8.442%	$164.3981	$164.40	$164.40	$164.40
7 purchase totals =	$1,264.97		$1,363.5578	$1,363.54	$1,363.55	$1,363.50