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	$184.33	6.579%	$196.4571	$196.46	$196.45	$196.50
Purchase #2	$88.28	7.506%	$94.9063	$94.91	$94.90	$94.90
Purchase #3	$153.30	4.319%	$159.921	$159.92	$159.90	$159.90
Purchase #4	$167.96	9.602%	$184.0875	$184.09	$184.10	$184.10
Purchase #5	$48.51	5.754%	$51.3013	$51.30	$51.30	$51.30
Purchase #6	$233.37	10.459%	$257.7782	$257.78	$257.80	$257.80
Purchase #7	$243.66	11.226%	$271.0133	$271.01	$271.00	$271.00
7 purchase totals =	$1,119.41		$1,215.4647	$1,215.47	$1,215.45	$1,215.50