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	$114.75	7.780%	$123.6776	$123.68	$123.70	$123.70
Purchase #2	$196.37	10.308%	$216.6118	$216.61	$216.60	$216.60
Purchase #3	$44.73	6.404%	$47.5945	$47.59	$47.60	$47.60
Purchase #4	$83.76	7.685%	$90.197	$90.20	$90.20	$90.20
Purchase #5	$194.51	11.723%	$217.3124	$217.31	$217.30	$217.30
Purchase #6	$59.63	5.305%	$62.7934	$62.79	$62.80	$62.80
Purchase #7	$198.26	3.765%	$205.7245	$205.72	$205.70	$205.70
7 purchase totals =	$892.01		$963.9112	$963.90	$963.90	$963.90