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	$194.32	9.861%	$213.4819	$213.48	$213.50	$213.50
Purchase #2	$84.55	13.660%	$96.0995	$96.10	$96.10	$96.10
Purchase #3	$203.48	10.333%	$224.5056	$224.51	$224.50	$224.50
Purchase #4	$100.71	10.259%	$111.0418	$111.04	$111.05	$111.00
Purchase #5	$65.94	13.472%	$74.8234	$74.82	$74.80	$74.80
Purchase #6	$119.99	3.503%	$124.1932	$124.19	$124.20	$124.20
Purchase #7	$68.51	3.801%	$71.1141	$71.11	$71.10	$71.10
7 purchase totals =	$837.50		$915.2595	$915.25	$915.25	$915.20