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	$90.76	11.255%	$100.975	$100.98	$101.00	$101.00
Purchase #2	$48.83	10.303%	$53.861	$53.86	$53.85	$53.90
Purchase #3	$101.57	12.863%	$114.6349	$114.63	$114.65	$114.60
Purchase #4	$107.65	7.160%	$115.3577	$115.36	$115.35	$115.40
Purchase #5	$114.50	7.425%	$123.0016	$123.00	$123.00	$123.00
Purchase #6	$30.81	7.689%	$33.179	$33.18	$33.20	$33.20
Purchase #7	$80.85	11.533%	$90.1744	$90.17	$90.15	$90.20
7 purchase totals =	$574.97		$631.1836	$631.18	$631.20	$631.30