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	$210.77	6.760%	$225.0181	$225.02	$225.00	$225.00
Purchase #2	$130.82	5.330%	$137.7927	$137.79	$137.80	$137.80
Purchase #3	$91.34	10.611%	$101.0321	$101.03	$101.05	$101.00
Purchase #4	$7.86	10.545%	$8.6888	$8.69	$8.70	$8.70
Purchase #5	$139.82	12.211%	$156.8934	$156.89	$156.90	$156.90
Purchase #6	$6.56	5.443%	$6.9171	$6.92	$6.90	$6.90
Purchase #7	$138.59	9.149%	$151.2696	$151.27	$151.25	$151.30
7 purchase totals =	$725.76		$787.6118	$787.61	$787.60	$787.60