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	$52.88	13.283%	$59.9041	$59.90	$59.90	$59.90
Purchase #2	$52.98	4.788%	$55.5167	$55.52	$55.50	$55.50
Purchase #3	$144.80	6.585%	$154.3351	$154.34	$154.35	$154.30
Purchase #4	$144.65	13.605%	$164.3296	$164.33	$164.35	$164.30
Purchase #5	$100.40	8.156%	$108.5886	$108.59	$108.60	$108.60
Purchase #6	$170.91	6.168%	$181.4517	$181.45	$181.45	$181.50
Purchase #7	$189.74	6.460%	$201.9972	$202.00	$202.00	$202.00
7 purchase totals =	$856.36		$926.1230	$926.13	$926.15	$926.10