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	$103.95	9.501%	$113.8263	$113.83	$113.85	$113.80
Purchase #2	$93.50	7.537%	$100.5471	$100.55	$100.55	$100.50
Purchase #3	$6.72	10.588%	$7.4315	$7.43	$7.45	$7.40
Purchase #4	$215.66	3.382%	$222.9536	$222.95	$222.95	$223.00
Purchase #5	$188.31	4.257%	$196.3264	$196.33	$196.35	$196.30
Purchase #6	$235.74	3.314%	$243.5524	$243.55	$243.55	$243.60
Purchase #7	$68.35	3.677%	$70.8632	$70.86	$70.85	$70.90
7 purchase totals =	$912.23		$955.5005	$955.50	$955.55	$955.50