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	$38.63	12.251%	$43.3626	$43.36	$43.35	$43.40
Purchase #2	$83.63	8.172%	$90.4642	$90.46	$90.45	$90.50
Purchase #3	$14.61	7.524%	$15.7093	$15.71	$15.70	$15.70
Purchase #4	$78.83	3.124%	$81.2926	$81.29	$81.30	$81.30
Purchase #5	$186.59	3.321%	$192.7867	$192.79	$192.80	$192.80
Purchase #6	$224.77	3.778%	$233.2618	$233.26	$233.25	$233.30
Purchase #7	$130.37	6.108%	$138.333	$138.33	$138.35	$138.30
7 purchase totals =	$757.43		$795.2102	$795.20	$795.20	$795.30