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	$157.81	4.223%	$164.4743	$164.47	$164.45	$164.50
Purchase #2	$162.83	8.123%	$176.0567	$176.06	$176.05	$176.10
Purchase #3	$236.72	8.500%	$256.8412	$256.84	$256.85	$256.80
Purchase #4	$231.48	4.271%	$241.3665	$241.37	$241.35	$241.40
Purchase #5	$96.48	10.190%	$106.3113	$106.31	$106.30	$106.30
Purchase #6	$162.76	13.756%	$185.1493	$185.15	$185.15	$185.10
Purchase #7	$93.94	3.604%	$97.3256	$97.33	$97.35	$97.30
7 purchase totals =	$1,142.02		$1,227.5249	$1,227.53	$1,227.50	$1,227.50