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	$187.82	12.484%	$211.2674	$211.27	$211.25	$211.30
Purchase #2	$39.80	4.142%	$41.4485	$41.45	$41.45	$41.40
Purchase #3	$95.43	6.432%	$101.5681	$101.57	$101.55	$101.60
Purchase #4	$91.39	9.348%	$99.9331	$99.93	$99.95	$99.90
Purchase #5	$73.33	9.867%	$80.5655	$80.57	$80.55	$80.60
Purchase #6	$39.29	11.451%	$43.7891	$43.79	$43.80	$43.80
Purchase #7	$48.37	3.682%	$50.151	$50.15	$50.15	$50.20
7 purchase totals =	$575.43		$628.7227	$628.73	$628.70	$628.80