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	$234.92	5.217%	$247.1758	$247.18	$247.20	$247.20
Purchase #2	$58.96	6.330%	$62.6922	$62.69	$62.70	$62.70
Purchase #3	$32.72	12.843%	$36.9222	$36.92	$36.90	$36.90
Purchase #4	$192.53	13.713%	$218.9316	$218.93	$218.95	$218.90
Purchase #5	$187.51	4.850%	$196.6042	$196.60	$196.60	$196.60
Purchase #6	$130.96	5.523%	$138.1929	$138.19	$138.20	$138.20
Purchase #7	$181.68	10.248%	$200.2986	$200.30	$200.30	$200.30
7 purchase totals =	$1,019.28		$1,100.8175	$1,100.81	$1,100.85	$1,100.80