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	$221.78	11.493%	$247.2692	$247.27	$247.25	$247.30
Purchase #2	$80.49	12.509%	$90.5585	$90.56	$90.55	$90.60
Purchase #3	$111.32	4.221%	$116.0188	$116.02	$116.00	$116.00
Purchase #4	$170.71	5.402%	$179.9318	$179.93	$179.95	$179.90
Purchase #5	$203.40	9.360%	$222.4382	$222.44	$222.45	$222.40
Purchase #6	$50.57	5.248%	$53.2239	$53.22	$53.20	$53.20
Purchase #7	$194.56	6.593%	$207.3873	$207.39	$207.40	$207.40
7 purchase totals =	$1,032.83		$1,116.8277	$1,116.83	$1,116.80	$1,116.80