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	$195.86	6.840%	$209.2568	$209.26	$209.25	$209.30
Purchase #2	$174.92	12.418%	$196.6416	$196.64	$196.65	$196.60
Purchase #3	$77.61	11.566%	$86.5864	$86.59	$86.60	$86.60
Purchase #4	$23.34	7.175%	$25.0146	$25.01	$25.00	$25.00
Purchase #5	$27.73	13.499%	$31.4733	$31.47	$31.45	$31.50
Purchase #6	$49.93	6.581%	$53.2159	$53.22	$53.20	$53.20
Purchase #7	$50.90	5.373%	$53.6349	$53.63	$53.65	$53.60
7 purchase totals =	$600.29		$655.8235	$655.82	$655.80	$655.80