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	$70.51	11.610%	$78.6962	$78.70	$78.70	$78.70
Purchase #2	$25.47	12.426%	$28.6349	$28.63	$28.65	$28.60
Purchase #3	$172.77	13.634%	$196.3255	$196.33	$196.35	$196.30
Purchase #4	$226.90	12.441%	$255.1286	$255.13	$255.15	$255.10
Purchase #5	$177.83	4.333%	$185.5354	$185.54	$185.55	$185.50
Purchase #6	$152.52	9.807%	$167.4776	$167.48	$167.50	$167.50
Purchase #7	$172.54	11.450%	$192.2958	$192.30	$192.30	$192.30
7 purchase totals =	$998.54		$1,104.0940	$1,104.11	$1,104.20	$1,104.00