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	$137.35	10.181%	$151.3336	$151.33	$151.35	$151.30
Purchase #2	$174.93	12.325%	$196.4901	$196.49	$196.50	$196.50
Purchase #3	$233.56	12.631%	$263.061	$263.06	$263.05	$263.10
Purchase #4	$186.38	3.380%	$192.6796	$192.68	$192.70	$192.70
Purchase #5	$116.72	13.487%	$132.462	$132.46	$132.45	$132.50
Purchase #6	$110.77	9.709%	$121.5247	$121.52	$121.50	$121.50
Purchase #7	$155.34	8.288%	$168.2146	$168.21	$168.20	$168.20
7 purchase totals =	$1,115.05		$1,225.7656	$1,225.75	$1,225.75	$1,225.80