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	$71.89	8.575%	$78.0546	$78.05	$78.05	$78.10
Purchase #2	$194.75	12.368%	$218.8367	$218.84	$218.85	$218.80
Purchase #3	$184.81	11.759%	$206.5418	$206.54	$206.55	$206.50
Purchase #4	$87.82	5.685%	$92.8126	$92.81	$92.80	$92.80
Purchase #5	$184.78	6.536%	$196.8572	$196.86	$196.85	$196.90
Purchase #6	$247.78	5.387%	$261.1279	$261.13	$261.15	$261.10
Purchase #7	$61.53	13.582%	$69.887	$69.89	$69.90	$69.90
7 purchase totals =	$1,033.36		$1,124.1178	$1,124.12	$1,124.15	$1,124.10