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	$110.35	13.788%	$125.5651	$125.57	$125.55	$125.60
Purchase #2	$207.56	7.209%	$222.523	$222.52	$222.50	$222.50
Purchase #3	$104.92	6.493%	$111.7325	$111.73	$111.75	$111.70
Purchase #4	$110.64	8.201%	$119.7136	$119.71	$119.70	$119.70
Purchase #5	$221.67	12.595%	$249.5893	$249.59	$249.60	$249.60
Purchase #6	$196.47	9.700%	$215.5276	$215.53	$215.55	$215.50
Purchase #7	$81.56	8.154%	$88.2104	$88.21	$88.20	$88.20
7 purchase totals =	$1,033.17		$1,132.8615	$1,132.86	$1,132.85	$1,132.80