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	$163.84	6.277%	$174.1242	$174.12	$174.10	$174.10
Purchase #2	$177.70	10.542%	$196.4331	$196.43	$196.45	$196.40
Purchase #3	$203.85	7.264%	$218.6577	$218.66	$218.65	$218.70
Purchase #4	$86.32	13.803%	$98.2347	$98.23	$98.25	$98.20
Purchase #5	$51.58	7.461%	$55.4284	$55.43	$55.45	$55.40
Purchase #6	$137.59	3.299%	$142.1291	$142.13	$142.15	$142.10
Purchase #7	$37.39	8.784%	$40.6743	$40.67	$40.65	$40.70
7 purchase totals =	$858.27		$925.6815	$925.67	$925.70	$925.60