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	$97.54	13.849%	$111.0483	$111.05	$111.05	$111.00
Purchase #2	$80.73	10.408%	$89.1324	$89.13	$89.15	$89.10
Purchase #3	$110.28	5.413%	$116.2495	$116.25	$116.25	$116.20
Purchase #4	$119.41	10.829%	$132.3409	$132.34	$132.35	$132.30
Purchase #5	$84.90	9.184%	$92.6972	$92.70	$92.70	$92.70
Purchase #6	$238.75	7.185%	$255.9042	$255.90	$255.90	$255.90
Purchase #7	$224.73	13.580%	$255.2483	$255.25	$255.25	$255.20
7 purchase totals =	$956.34		$1,052.6208	$1,052.62	$1,052.65	$1,052.40