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	$118.37	8.195%	$128.0704	$128.07	$128.05	$128.10
Purchase #2	$171.61	11.380%	$191.1392	$191.14	$191.15	$191.10
Purchase #3	$176.88	11.324%	$196.9099	$196.91	$196.90	$196.90
Purchase #4	$101.60	13.608%	$115.4257	$115.43	$115.45	$115.40
Purchase #5	$20.81	5.506%	$21.9558	$21.96	$21.95	$22.00
Purchase #6	$233.37	11.124%	$259.3301	$259.33	$259.35	$259.30
Purchase #7	$56.77	11.787%	$63.4615	$63.46	$63.45	$63.50
7 purchase totals =	$879.41		$976.2926	$976.30	$976.30	$976.30