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	$117.47	5.829%	$124.3173	$124.32	$124.30	$124.30
Purchase #2	$43.61	5.321%	$45.9305	$45.93	$45.95	$45.90
Purchase #3	$101.28	7.754%	$109.1333	$109.13	$109.15	$109.10
Purchase #4	$131.85	3.473%	$136.4292	$136.43	$136.45	$136.40
Purchase #5	$184.55	12.824%	$208.2167	$208.22	$208.20	$208.20
Purchase #6	$180.77	4.127%	$188.2304	$188.23	$188.25	$188.20
Purchase #7	$94.57	5.537%	$99.8063	$99.81	$99.80	$99.80
7 purchase totals =	$854.10		$912.0637	$912.07	$912.10	$911.90