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	$187.40	4.820%	$196.4327	$196.43	$196.45	$196.40
Purchase #2	$131.78	4.429%	$137.6165	$137.62	$137.60	$137.60
Purchase #3	$125.39	13.106%	$141.8236	$141.82	$141.80	$141.80
Purchase #4	$190.43	11.862%	$213.0188	$213.02	$213.00	$213.00
Purchase #5	$79.32	8.816%	$86.3129	$86.31	$86.30	$86.30
Purchase #6	$151.48	8.476%	$164.3194	$164.32	$164.30	$164.30
Purchase #7	$203.64	8.768%	$221.4952	$221.50	$221.50	$221.50
7 purchase totals =	$1,069.44		$1,161.0191	$1,161.02	$1,160.95	$1,160.90