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	$202.78	9.874%	$222.8025	$222.80	$222.80	$222.80
Purchase #2	$195.97	13.561%	$222.5455	$222.55	$222.55	$222.50
Purchase #3	$217.74	3.167%	$224.6358	$224.64	$224.65	$224.60
Purchase #4	$42.83	5.333%	$45.1141	$45.11	$45.10	$45.10
Purchase #5	$199.93	5.266%	$210.4583	$210.46	$210.45	$210.50
Purchase #6	$52.73	6.832%	$56.3325	$56.33	$56.35	$56.30
Purchase #7	$29.47	6.542%	$31.3979	$31.40	$31.40	$31.40
7 purchase totals =	$941.45		$1,013.2866	$1,013.29	$1,013.30	$1,013.20