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	$104.46	7.151%	$111.9299	$111.93	$111.95	$111.90
Purchase #2	$14.45	4.805%	$15.1443	$15.14	$15.15	$15.10
Purchase #3	$7.84	12.172%	$8.7943	$8.79	$8.80	$8.80
Purchase #4	$177.58	10.788%	$196.7373	$196.74	$196.75	$196.70
Purchase #5	$113.89	8.404%	$123.4613	$123.46	$123.45	$123.50
Purchase #6	$167.74	8.709%	$182.3485	$182.35	$182.35	$182.30
Purchase #7	$171.96	13.740%	$195.5873	$195.59	$195.60	$195.60
7 purchase totals =	$757.92		$834.0029	$834.00	$834.05	$833.90