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	$33.98	9.309%	$37.1432	$37.14	$37.15	$37.10
Purchase #2	$15.77	8.451%	$17.1027	$17.10	$17.10	$17.10
Purchase #3	$90.79	13.827%	$103.3435	$103.34	$103.35	$103.30
Purchase #4	$238.70	6.450%	$254.0962	$254.10	$254.10	$254.10
Purchase #5	$181.86	9.712%	$199.5222	$199.52	$199.50	$199.50
Purchase #6	$41.33	13.308%	$46.8302	$46.83	$46.85	$46.80
Purchase #7	$110.54	5.116%	$116.1952	$116.20	$116.20	$116.20
7 purchase totals =	$712.97		$774.2332	$774.23	$774.25	$774.10