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	$113.80	3.771%	$118.0914	$118.09	$118.10	$118.10
Purchase #2	$163.81	11.347%	$182.3975	$182.40	$182.40	$182.40
Purchase #3	$141.80	13.442%	$160.8608	$160.86	$160.85	$160.90
Purchase #4	$209.80	8.651%	$227.9498	$227.95	$227.95	$227.90
Purchase #5	$181.38	6.109%	$192.4605	$192.46	$192.45	$192.50
Purchase #6	$121.54	4.830%	$127.4104	$127.41	$127.40	$127.40
Purchase #7	$181.70	3.121%	$187.3709	$187.37	$187.35	$187.40
7 purchase totals =	$1,113.83		$1,196.5413	$1,196.54	$1,196.50	$1,196.60