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	$184.49	7.810%	$198.8987	$198.90	$198.90	$198.90
Purchase #2	$211.40	6.715%	$225.5955	$225.60	$225.60	$225.60
Purchase #3	$115.29	3.669%	$119.52	$119.52	$119.50	$119.50
Purchase #4	$153.48	12.578%	$172.7847	$172.78	$172.80	$172.80
Purchase #5	$125.84	5.199%	$132.3824	$132.38	$132.40	$132.40
Purchase #6	$13.69	13.476%	$15.5349	$15.53	$15.55	$15.50
Purchase #7	$159.36	7.768%	$171.7391	$171.74	$171.75	$171.70
7 purchase totals =	$963.55		$1,036.4553	$1,036.45	$1,036.50	$1,036.40