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	$215.33	8.266%	$233.1292	$233.13	$233.15	$233.10
Purchase #2	$28.30	11.242%	$31.4815	$31.48	$31.50	$31.50
Purchase #3	$122.58	4.549%	$128.1562	$128.16	$128.15	$128.20
Purchase #4	$219.61	4.554%	$229.611	$229.61	$229.60	$229.60
Purchase #5	$100.94	13.143%	$114.2065	$114.21	$114.20	$114.20
Purchase #6	$240.61	3.663%	$249.4235	$249.42	$249.40	$249.40
Purchase #7	$20.57	4.485%	$21.4926	$21.49	$21.50	$21.50
7 purchase totals =	$947.94		$1,007.5005	$1,007.50	$1,007.50	$1,007.50