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	$68.95	10.390%	$76.1139	$76.11	$76.10	$76.10
Purchase #2	$94.96	7.580%	$102.158	$102.16	$102.15	$102.20
Purchase #3	$41.84	3.298%	$43.2199	$43.22	$43.20	$43.20
Purchase #4	$128.56	9.545%	$140.8311	$140.83	$140.85	$140.80
Purchase #5	$191.90	4.381%	$200.3071	$200.31	$200.30	$200.30
Purchase #6	$12.51	8.617%	$13.588	$13.59	$13.60	$13.60
Purchase #7	$240.66	5.506%	$253.9107	$253.91	$253.90	$253.90
7 purchase totals =	$779.38		$830.1287	$830.13	$830.10	$830.10