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	$51.55	7.540%	$55.4369	$55.44	$55.45	$55.40
Purchase #2	$224.89	11.241%	$250.1699	$250.17	$250.15	$250.20
Purchase #3	$65.43	10.271%	$72.1503	$72.15	$72.15	$72.20
Purchase #4	$152.76	7.755%	$164.6065	$164.61	$164.60	$164.60
Purchase #5	$123.89	5.691%	$130.9406	$130.94	$130.95	$130.90
Purchase #6	$97.80	3.391%	$101.1164	$101.12	$101.10	$101.10
Purchase #7	$93.85	3.406%	$97.0465	$97.05	$97.05	$97.00
7 purchase totals =	$810.17		$871.4671	$871.48	$871.45	$871.40