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	$80.73	5.299%	$85.0079	$85.01	$85.00	$85.00
Purchase #2	$111.48	6.322%	$118.5278	$118.53	$118.55	$118.50
Purchase #3	$222.55	4.188%	$231.8704	$231.87	$231.85	$231.90
Purchase #4	$98.58	4.846%	$103.3572	$103.36	$103.35	$103.40
Purchase #5	$161.70	12.725%	$182.2763	$182.28	$182.30	$182.30
Purchase #6	$172.47	4.556%	$180.3277	$180.33	$180.35	$180.30
Purchase #7	$185.97	3.467%	$192.4176	$192.42	$192.40	$192.40
7 purchase totals =	$1,033.48		$1,093.7849	$1,093.80	$1,093.80	$1,093.80