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	$137.25	3.513%	$142.0716	$142.07	$142.05	$142.10
Purchase #2	$174.84	11.495%	$194.9379	$194.94	$194.95	$194.90
Purchase #3	$177.66	4.505%	$185.6636	$185.66	$185.65	$185.70
Purchase #4	$205.37	8.414%	$222.6498	$222.65	$222.65	$222.60
Purchase #5	$56.62	3.237%	$58.4528	$58.45	$58.45	$58.50
Purchase #6	$83.63	8.229%	$90.5119	$90.51	$90.50	$90.50
Purchase #7	$115.52	9.726%	$126.7555	$126.76	$126.75	$126.80
7 purchase totals =	$950.89		$1,021.0431	$1,021.04	$1,021.00	$1,021.10