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	$218.76	3.870%	$227.226	$227.23	$227.25	$227.20
Purchase #2	$210.54	6.354%	$223.9177	$223.92	$223.90	$223.90
Purchase #3	$93.84	7.504%	$100.8818	$100.88	$100.90	$100.90
Purchase #4	$88.38	7.749%	$95.2286	$95.23	$95.25	$95.20
Purchase #5	$11.75	9.590%	$12.8768	$12.88	$12.90	$12.90
Purchase #6	$93.44	4.684%	$97.8167	$97.82	$97.80	$97.80
Purchase #7	$103.40	13.680%	$117.5451	$117.55	$117.55	$117.50
7 purchase totals =	$820.11		$875.4927	$875.51	$875.55	$875.40