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	$43.40	7.587%	$46.6928	$46.69	$46.70	$46.70
Purchase #2	$186.69	6.334%	$198.5149	$198.51	$198.50	$198.50
Purchase #3	$63.85	3.538%	$66.109	$66.11	$66.10	$66.10
Purchase #4	$98.32	11.835%	$109.9562	$109.96	$109.95	$110.00
Purchase #5	$229.30	4.645%	$239.951	$239.95	$239.95	$240.00
Purchase #6	$219.34	3.612%	$227.2626	$227.26	$227.25	$227.30
Purchase #7	$99.42	12.467%	$111.8147	$111.81	$111.80	$111.80
7 purchase totals =	$940.32		$1,000.3012	$1,000.29	$1,000.25	$1,000.40