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	$99.44	13.526%	$112.8903	$112.89	$112.90	$112.90
Purchase #2	$50.98	4.431%	$53.2389	$53.24	$53.25	$53.20
Purchase #3	$130.76	7.299%	$140.3042	$140.30	$140.30	$140.30
Purchase #4	$80.72	9.527%	$88.4102	$88.41	$88.40	$88.40
Purchase #5	$178.83	7.529%	$192.2941	$192.29	$192.30	$192.30
Purchase #6	$131.40	10.182%	$144.7791	$144.78	$144.80	$144.80
Purchase #7	$118.40	11.146%	$131.5969	$131.60	$131.60	$131.60
7 purchase totals =	$790.53		$863.5137	$863.51	$863.55	$863.50