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	$70.96	10.572%	$78.4619	$78.46	$78.45	$78.50
Purchase #2	$119.54	10.302%	$131.855	$131.86	$131.85	$131.90
Purchase #3	$79.26	8.405%	$85.9218	$85.92	$85.90	$85.90
Purchase #4	$111.75	13.178%	$126.4764	$126.48	$126.50	$126.50
Purchase #5	$43.57	7.388%	$46.789	$46.79	$46.80	$46.80
Purchase #6	$151.81	10.600%	$167.9019	$167.90	$167.90	$167.90
Purchase #7	$155.80	5.813%	$164.8567	$164.86	$164.85	$164.90
7 purchase totals =	$732.69		$802.2627	$802.27	$802.25	$802.40