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	$149.81	11.500%	$167.0382	$167.04	$167.05	$167.00
Purchase #2	$81.39	12.352%	$91.4433	$91.44	$91.45	$91.40
Purchase #3	$40.80	13.681%	$46.3818	$46.38	$46.40	$46.40
Purchase #4	$156.80	3.532%	$162.3382	$162.34	$162.35	$162.30
Purchase #5	$51.62	6.473%	$54.9614	$54.96	$54.95	$55.00
Purchase #6	$241.45	12.330%	$271.2208	$271.22	$271.20	$271.20
Purchase #7	$43.95	3.291%	$45.3964	$45.40	$45.40	$45.40
7 purchase totals =	$765.82		$838.7801	$838.78	$838.80	$838.70