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	$44.45	4.818%	$46.5916	$46.59	$46.60	$46.60
Purchase #2	$70.32	12.199%	$78.8983	$78.90	$78.90	$78.90
Purchase #3	$230.53	10.733%	$255.2728	$255.27	$255.25	$255.30
Purchase #4	$239.52	6.170%	$254.2984	$254.30	$254.30	$254.30
Purchase #5	$135.80	12.866%	$153.272	$153.27	$153.25	$153.30
Purchase #6	$37.47	3.710%	$38.8601	$38.86	$38.85	$38.90
Purchase #7	$119.96	5.678%	$126.7713	$126.77	$126.75	$126.80
7 purchase totals =	$878.05		$953.9645	$953.96	$953.90	$954.10