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	$65.73	12.718%	$74.0895	$74.09	$74.10	$74.10
Purchase #2	$71.90	9.321%	$78.6018	$78.60	$78.60	$78.60
Purchase #3	$43.64	4.673%	$45.6793	$45.68	$45.70	$45.70
Purchase #4	$231.83	10.598%	$256.3993	$256.40	$256.40	$256.40
Purchase #5	$65.42	8.617%	$71.0572	$71.06	$71.05	$71.10
Purchase #6	$115.97	7.293%	$124.4277	$124.43	$124.45	$124.40
Purchase #7	$103.92	10.529%	$114.8617	$114.86	$114.85	$114.90
7 purchase totals =	$698.41		$765.1165	$765.12	$765.15	$765.20