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	$114.59	13.476%	$130.0321	$130.03	$130.05	$130.00
Purchase #2	$82.30	9.258%	$89.9193	$89.92	$89.90	$89.90
Purchase #3	$76.87	6.720%	$82.0357	$82.04	$82.05	$82.00
Purchase #4	$177.46	10.716%	$196.4766	$196.48	$196.50	$196.50
Purchase #5	$80.58	13.865%	$91.7524	$91.75	$91.75	$91.80
Purchase #6	$202.55	11.412%	$225.665	$225.67	$225.65	$225.70
Purchase #7	$177.84	8.276%	$192.558	$192.56	$192.55	$192.60
7 purchase totals =	$912.19		$1,008.4391	$1,008.45	$1,008.45	$1,008.50