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	$95.71	11.140%	$106.3721	$106.37	$106.35	$106.40
Purchase #2	$203.83	9.689%	$223.5791	$223.58	$223.60	$223.60
Purchase #3	$100.71	8.772%	$109.5443	$109.54	$109.55	$109.50
Purchase #4	$52.57	9.361%	$57.4911	$57.49	$57.50	$57.50
Purchase #5	$164.76	7.189%	$176.6046	$176.60	$176.60	$176.60
Purchase #6	$39.35	7.140%	$42.1596	$42.16	$42.15	$42.20
Purchase #7	$243.49	7.312%	$261.294	$261.29	$261.30	$261.30
7 purchase totals =	$900.42		$977.0448	$977.03	$977.05	$977.10