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	$109.72	13.439%	$124.4653	$124.47	$124.45	$124.50
Purchase #2	$205.27	8.836%	$223.4077	$223.41	$223.40	$223.40
Purchase #3	$113.98	9.848%	$125.2048	$125.20	$125.20	$125.20
Purchase #4	$81.25	10.693%	$89.9381	$89.94	$89.95	$89.90
Purchase #5	$231.92	7.747%	$249.8868	$249.89	$249.90	$249.90
Purchase #6	$88.51	13.464%	$100.427	$100.43	$100.45	$100.40
Purchase #7	$96.76	12.276%	$108.6383	$108.64	$108.65	$108.60
7 purchase totals =	$927.41		$1,021.9680	$1,021.98	$1,022.00	$1,021.90