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	$203.86	6.706%	$217.5309	$217.53	$217.55	$217.50
Purchase #2	$201.38	6.245%	$213.9562	$213.96	$213.95	$214.00
Purchase #3	$174.38	10.702%	$193.0421	$193.04	$193.05	$193.00
Purchase #4	$195.78	5.144%	$205.8509	$205.85	$205.85	$205.90
Purchase #5	$206.48	7.589%	$222.1498	$222.15	$222.15	$222.10
Purchase #6	$59.46	9.869%	$65.3281	$65.33	$65.35	$65.30
Purchase #7	$200.30	11.277%	$222.8878	$222.89	$222.90	$222.90
7 purchase totals =	$1,241.64		$1,340.7458	$1,340.75	$1,340.80	$1,340.70