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	$156.96	9.812%	$172.3609	$172.36	$172.35	$172.40
Purchase #2	$6.53	10.131%	$7.1916	$7.19	$7.20	$7.20
Purchase #3	$79.65	6.575%	$84.887	$84.89	$84.90	$84.90
Purchase #4	$156.25	10.342%	$172.4094	$172.41	$172.40	$172.40
Purchase #5	$109.41	10.295%	$120.6738	$120.67	$120.65	$120.70
Purchase #6	$242.51	5.152%	$255.0041	$255.00	$255.00	$255.00
Purchase #7	$246.85	4.725%	$258.5137	$258.51	$258.50	$258.50
7 purchase totals =	$998.16		$1,071.0405	$1,071.03	$1,071.00	$1,071.10