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	$225.33	9.112%	$245.8621	$245.86	$245.85	$245.90
Purchase #2	$195.94	6.776%	$209.2169	$209.22	$209.20	$209.20
Purchase #3	$223.33	3.437%	$231.0059	$231.01	$231.00	$231.00
Purchase #4	$120.75	8.763%	$131.3313	$131.33	$131.35	$131.30
Purchase #5	$199.61	6.183%	$211.9519	$211.95	$211.95	$212.00
Purchase #6	$63.96	5.679%	$67.5923	$67.59	$67.60	$67.60
Purchase #7	$12.35	4.769%	$12.939	$12.94	$12.95	$12.90
7 purchase totals =	$1,041.27		$1,109.8994	$1,109.90	$1,109.90	$1,109.90