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	$133.83	11.272%	$148.9153	$148.92	$148.90	$148.90
Purchase #2	$85.25	6.851%	$91.0905	$91.09	$91.10	$91.10
Purchase #3	$203.39	8.410%	$220.4951	$220.50	$220.50	$220.50
Purchase #4	$233.80	3.700%	$242.4506	$242.45	$242.45	$242.50
Purchase #5	$37.25	11.497%	$41.5326	$41.53	$41.55	$41.50
Purchase #6	$38.67	12.384%	$43.4589	$43.46	$43.45	$43.50
Purchase #7	$233.91	12.231%	$262.5195	$262.52	$262.50	$262.50
7 purchase totals =	$966.10		$1,050.4625	$1,050.47	$1,050.45	$1,050.50