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	$61.37	5.675%	$64.8527	$64.85	$64.85	$64.90
Purchase #2	$40.91	12.302%	$45.9427	$45.94	$45.95	$45.90
Purchase #3	$189.54	11.611%	$211.5475	$211.55	$211.55	$211.50
Purchase #4	$111.47	4.338%	$116.3056	$116.31	$116.30	$116.30
Purchase #5	$67.91	4.564%	$71.0094	$71.01	$71.00	$71.00
Purchase #6	$193.76	10.137%	$213.4015	$213.40	$213.40	$213.40
Purchase #7	$149.68	9.850%	$164.4235	$164.42	$164.40	$164.40
7 purchase totals =	$814.64		$887.4829	$887.48	$887.45	$887.40