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	$222.90	4.238%	$232.3465	$232.35	$232.35	$232.30
Purchase #2	$153.99	9.158%	$168.0924	$168.09	$168.10	$168.10
Purchase #3	$66.63	8.398%	$72.2256	$72.23	$72.25	$72.20
Purchase #4	$25.96	6.321%	$27.6009	$27.60	$27.60	$27.60
Purchase #5	$38.66	13.227%	$43.7736	$43.77	$43.75	$43.80
Purchase #6	$110.42	11.288%	$122.8842	$122.88	$122.90	$122.90
Purchase #7	$52.78	11.853%	$59.036	$59.04	$59.05	$59.00
7 purchase totals =	$671.34		$725.9592	$725.96	$726.00	$725.90