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	$69.58	3.802%	$72.2254	$72.23	$72.25	$72.20
Purchase #2	$213.41	3.418%	$220.7044	$220.70	$220.70	$220.70
Purchase #3	$17.82	10.584%	$19.7061	$19.71	$19.70	$19.70
Purchase #4	$132.51	3.152%	$136.6867	$136.69	$136.70	$136.70
Purchase #5	$75.40	6.850%	$80.5649	$80.56	$80.55	$80.60
Purchase #6	$72.29	13.406%	$81.9812	$81.98	$82.00	$82.00
Purchase #7	$85.95	4.296%	$89.6424	$89.64	$89.65	$89.60
7 purchase totals =	$666.96		$701.5111	$701.51	$701.55	$701.50