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	$233.49	13.332%	$264.6189	$264.62	$264.60	$264.60
Purchase #2	$154.43	11.317%	$171.9068	$171.91	$171.90	$171.90
Purchase #3	$220.97	8.725%	$240.2496	$240.25	$240.25	$240.20
Purchase #4	$78.82	5.234%	$82.9454	$82.95	$82.95	$82.90
Purchase #5	$65.89	6.641%	$70.2658	$70.27	$70.25	$70.30
Purchase #6	$180.69	5.693%	$190.9767	$190.98	$191.00	$191.00
Purchase #7	$199.40	6.270%	$211.9024	$211.90	$211.90	$211.90
7 purchase totals =	$1,133.69		$1,232.8656	$1,232.88	$1,232.85	$1,232.80