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	$208.56	6.814%	$222.7713	$222.77	$222.75	$222.80
Purchase #2	$174.48	4.343%	$182.0577	$182.06	$182.05	$182.10
Purchase #3	$127.47	6.694%	$136.0028	$136.00	$136.00	$136.00
Purchase #4	$212.35	5.140%	$223.2648	$223.26	$223.25	$223.30
Purchase #5	$78.86	5.299%	$83.0388	$83.04	$83.05	$83.00
Purchase #6	$54.85	3.841%	$56.9568	$56.96	$56.95	$57.00
Purchase #7	$38.81	10.587%	$42.9188	$42.92	$42.90	$42.90
7 purchase totals =	$895.38		$947.0110	$947.01	$946.95	$947.10