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	$116.75	12.465%	$131.3029	$131.30	$131.30	$131.30
Purchase #2	$127.75	6.143%	$135.5977	$135.60	$135.60	$135.60
Purchase #3	$137.72	9.735%	$151.127	$151.13	$151.15	$151.10
Purchase #4	$106.77	9.704%	$117.131	$117.13	$117.15	$117.10
Purchase #5	$77.33	10.594%	$85.5223	$85.52	$85.50	$85.50
Purchase #6	$122.71	3.239%	$126.6846	$126.68	$126.70	$126.70
Purchase #7	$34.87	6.803%	$37.2422	$37.24	$37.25	$37.20
7 purchase totals =	$723.90		$784.6077	$784.60	$784.65	$784.50