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	$57.95	9.853%	$63.6598	$63.66	$63.65	$63.70
Purchase #2	$122.55	4.614%	$128.2045	$128.20	$128.20	$128.20
Purchase #3	$42.94	6.421%	$45.6972	$45.70	$45.70	$45.70
Purchase #4	$85.25	4.682%	$89.2414	$89.24	$89.25	$89.20
Purchase #5	$18.84	13.201%	$21.3271	$21.33	$21.35	$21.30
Purchase #6	$193.82	3.423%	$200.4545	$200.45	$200.45	$200.50
Purchase #7	$143.79	13.306%	$162.9227	$162.92	$162.90	$162.90
7 purchase totals =	$665.14		$711.5072	$711.50	$711.50	$711.50