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	$178.81	6.239%	$189.966	$189.97	$189.95	$190.00
Purchase #2	$166.87	12.821%	$188.2644	$188.26	$188.25	$188.30
Purchase #3	$6.82	9.490%	$7.4672	$7.47	$7.45	$7.50
Purchase #4	$203.85	12.552%	$229.4373	$229.44	$229.45	$229.40
Purchase #5	$41.33	10.822%	$45.8027	$45.80	$45.80	$45.80
Purchase #6	$199.60	4.218%	$208.0191	$208.02	$208.00	$208.00
Purchase #7	$179.97	5.816%	$190.4371	$190.44	$190.45	$190.40
7 purchase totals =	$977.25		$1,059.3938	$1,059.40	$1,059.35	$1,059.40