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	$142.76	9.326%	$156.0738	$156.07	$156.05	$156.10
Purchase #2	$143.69	9.241%	$156.9684	$156.97	$156.95	$157.00
Purchase #3	$234.79	6.270%	$249.5113	$249.51	$249.50	$249.50
Purchase #4	$9.86	13.857%	$11.2263	$11.23	$11.25	$11.20
Purchase #5	$174.88	7.808%	$188.5346	$188.53	$188.55	$188.50
Purchase #6	$99.41	6.464%	$105.8359	$105.84	$105.85	$105.80
Purchase #7	$212.60	11.741%	$237.5614	$237.56	$237.55	$237.60
7 purchase totals =	$1,017.99		$1,105.7117	$1,105.71	$1,105.70	$1,105.70