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	$88.25	12.526%	$99.3042	$99.30	$99.30	$99.30
Purchase #2	$50.81	10.222%	$56.0038	$56.00	$56.00	$56.00
Purchase #3	$54.35	9.660%	$59.6002	$59.60	$59.60	$59.60
Purchase #4	$41.63	5.586%	$43.9555	$43.96	$43.95	$44.00
Purchase #5	$111.59	6.537%	$118.8846	$118.88	$118.90	$118.90
Purchase #6	$211.73	3.450%	$219.0347	$219.03	$219.05	$219.00
Purchase #7	$17.29	11.225%	$19.2308	$19.23	$19.25	$19.20
7 purchase totals =	$575.65		$616.0138	$616.00	$616.05	$616.00