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	$118.40	10.835%	$131.2286	$131.23	$131.25	$131.20
Purchase #2	$126.74	10.326%	$139.8272	$139.83	$139.85	$139.80
Purchase #3	$201.51	10.291%	$222.2474	$222.25	$222.25	$222.20
Purchase #4	$146.26	6.158%	$155.2667	$155.27	$155.25	$155.30
Purchase #5	$182.83	7.201%	$195.9956	$196.00	$196.00	$196.00
Purchase #6	$163.27	7.690%	$175.8255	$175.83	$175.85	$175.80
Purchase #7	$218.60	11.133%	$242.9367	$242.94	$242.95	$242.90
7 purchase totals =	$1,157.61		$1,263.3277	$1,263.35	$1,263.40	$1,263.20