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	$105.79	10.359%	$116.7488	$116.75	$116.75	$116.70
Purchase #2	$247.29	4.144%	$257.5377	$257.54	$257.55	$257.50
Purchase #3	$176.64	11.824%	$197.5259	$197.53	$197.55	$197.50
Purchase #4	$111.38	12.475%	$125.2747	$125.27	$125.25	$125.30
Purchase #5	$65.25	6.166%	$69.2733	$69.27	$69.25	$69.30
Purchase #6	$82.82	9.433%	$90.6324	$90.63	$90.65	$90.60
Purchase #7	$142.46	11.216%	$158.4383	$158.44	$158.45	$158.40
7 purchase totals =	$931.63		$1,015.4311	$1,015.43	$1,015.45	$1,015.30