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	$214.43	6.273%	$227.8812	$227.88	$227.90	$227.90
Purchase #2	$85.54	5.487%	$90.2336	$90.23	$90.25	$90.20
Purchase #3	$5.28	13.842%	$6.0109	$6.01	$6.00	$6.00
Purchase #4	$99.31	10.290%	$109.529	$109.53	$109.55	$109.50
Purchase #5	$207.31	5.436%	$218.5794	$218.58	$218.60	$218.60
Purchase #6	$107.96	3.418%	$111.6501	$111.65	$111.65	$111.70
Purchase #7	$234.60	13.711%	$266.766	$266.77	$266.75	$266.80
7 purchase totals =	$954.43		$1,030.6502	$1,030.65	$1,030.70	$1,030.70