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	$83.96	12.225%	$94.2241	$94.22	$94.20	$94.20
Purchase #2	$135.83	13.148%	$153.6889	$153.69	$153.70	$153.70
Purchase #3	$93.42	3.225%	$96.4328	$96.43	$96.45	$96.40
Purchase #4	$214.45	13.124%	$242.5944	$242.59	$242.60	$242.60
Purchase #5	$148.81	5.168%	$156.5005	$156.50	$156.50	$156.50
Purchase #6	$80.74	10.348%	$89.095	$89.10	$89.10	$89.10
Purchase #7	$228.60	8.652%	$248.3785	$248.38	$248.40	$248.40
7 purchase totals =	$985.81		$1,080.9142	$1,080.91	$1,080.95	$1,080.90