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	$143.46	7.278%	$153.901	$153.90	$153.90	$153.90
Purchase #2	$119.99	13.753%	$136.4922	$136.49	$136.50	$136.50
Purchase #3	$72.82	13.726%	$82.8153	$82.82	$82.80	$82.80
Purchase #4	$160.94	3.455%	$166.5005	$166.50	$166.50	$166.50
Purchase #5	$196.64	13.570%	$223.324	$223.32	$223.30	$223.30
Purchase #6	$41.73	12.688%	$47.0247	$47.02	$47.00	$47.00
Purchase #7	$112.75	3.767%	$116.9973	$117.00	$117.00	$117.00
7 purchase totals =	$848.33		$927.0550	$927.05	$927.00	$927.00