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	$46.78	11.235%	$52.0357	$52.04	$52.05	$52.00
Purchase #2	$117.61	11.316%	$130.9187	$130.92	$130.90	$130.90
Purchase #3	$123.55	6.676%	$131.7982	$131.80	$131.80	$131.80
Purchase #4	$219.77	12.148%	$246.4677	$246.47	$246.45	$246.50
Purchase #5	$64.42	3.679%	$66.79	$66.79	$66.80	$66.80
Purchase #6	$174.33	5.828%	$184.49	$184.49	$184.50	$184.50
Purchase #7	$243.64	10.442%	$269.0809	$269.08	$269.10	$269.10
7 purchase totals =	$990.10		$1,081.5812	$1,081.59	$1,081.60	$1,081.60