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	$206.76	5.327%	$217.7741	$217.77	$217.75	$217.80
Purchase #2	$178.78	4.246%	$186.371	$186.37	$186.35	$186.40
Purchase #3	$246.62	11.267%	$274.4067	$274.41	$274.40	$274.40
Purchase #4	$92.86	4.600%	$97.1316	$97.13	$97.15	$97.10
Purchase #5	$86.52	13.828%	$98.484	$98.48	$98.50	$98.50
Purchase #6	$98.81	13.237%	$111.8895	$111.89	$111.90	$111.90
Purchase #7	$66.73	6.207%	$70.8719	$70.87	$70.85	$70.90
7 purchase totals =	$977.08		$1,056.9288	$1,056.92	$1,056.90	$1,057.00