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	$57.43	10.831%	$63.6502	$63.65	$63.65	$63.70
Purchase #2	$129.92	12.437%	$146.0782	$146.08	$146.10	$146.10
Purchase #3	$109.49	3.668%	$113.5061	$113.51	$113.50	$113.50
Purchase #4	$156.78	7.217%	$168.0948	$168.09	$168.10	$168.10
Purchase #5	$123.41	4.297%	$128.7129	$128.71	$128.70	$128.70
Purchase #6	$62.50	8.190%	$67.6188	$67.62	$67.60	$67.60
Purchase #7	$153.94	6.597%	$164.0954	$164.10	$164.10	$164.10
7 purchase totals =	$793.47		$851.7564	$851.76	$851.75	$851.80