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	$245.62	9.402%	$268.7132	$268.71	$268.70	$268.70
Purchase #2	$69.67	13.303%	$78.9382	$78.94	$78.95	$78.90
Purchase #3	$126.52	7.849%	$136.4506	$136.45	$136.45	$136.50
Purchase #4	$197.38	12.798%	$222.6407	$222.64	$222.65	$222.60
Purchase #5	$20.29	8.821%	$22.0798	$22.08	$22.10	$22.10
Purchase #6	$59.71	4.489%	$62.3904	$62.39	$62.40	$62.40
Purchase #7	$195.30	9.337%	$213.5352	$213.54	$213.55	$213.50
7 purchase totals =	$914.49		$1,004.7481	$1,004.75	$1,004.80	$1,004.70