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	$140.25	11.425%	$156.2736	$156.27	$156.25	$156.30
Purchase #2	$12.76	5.741%	$13.4926	$13.49	$13.50	$13.50
Purchase #3	$147.55	7.449%	$158.541	$158.54	$158.55	$158.50
Purchase #4	$42.88	11.263%	$47.7096	$47.71	$47.70	$47.70
Purchase #5	$138.95	4.755%	$145.5571	$145.56	$145.55	$145.60
Purchase #6	$44.77	6.767%	$47.7996	$47.80	$47.80	$47.80
Purchase #7	$135.56	6.622%	$144.5368	$144.54	$144.55	$144.50
7 purchase totals =	$662.72		$713.9103	$713.91	$713.90	$713.90