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	$56.59	12.324%	$63.5642	$63.56	$63.55	$63.60
Purchase #2	$151.37	13.792%	$172.247	$172.25	$172.25	$172.20
Purchase #3	$86.36	13.458%	$97.9823	$97.98	$98.00	$98.00
Purchase #4	$194.55	7.375%	$208.8981	$208.90	$208.90	$208.90
Purchase #5	$22.29	5.308%	$23.4732	$23.47	$23.45	$23.50
Purchase #6	$167.83	13.600%	$190.6549	$190.65	$190.65	$190.70
Purchase #7	$81.98	9.320%	$89.6205	$89.62	$89.60	$89.60
7 purchase totals =	$760.97		$846.4402	$846.43	$846.40	$846.50