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	$203.63	9.326%	$222.6205	$222.62	$222.60	$222.60
Purchase #2	$206.76	11.210%	$229.9378	$229.94	$229.95	$229.90
Purchase #3	$214.37	3.225%	$221.2834	$221.28	$221.30	$221.30
Purchase #4	$41.64	8.502%	$45.1802	$45.18	$45.20	$45.20
Purchase #5	$99.40	11.648%	$110.9781	$110.98	$111.00	$111.00
Purchase #6	$187.78	3.338%	$194.0481	$194.05	$194.05	$194.00
Purchase #7	$94.36	5.828%	$99.8593	$99.86	$99.85	$99.90
7 purchase totals =	$1,047.94		$1,123.9074	$1,123.91	$1,123.95	$1,123.90