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	$136.65	5.736%	$144.4882	$144.49	$144.50	$144.50
Purchase #2	$153.86	5.647%	$162.5485	$162.55	$162.55	$162.50
Purchase #3	$197.96	9.524%	$216.8137	$216.81	$216.80	$216.80
Purchase #4	$131.40	7.873%	$141.7451	$141.75	$141.75	$141.70
Purchase #5	$48.89	13.302%	$55.3933	$55.39	$55.40	$55.40
Purchase #6	$25.92	4.810%	$27.1668	$27.17	$27.15	$27.20
Purchase #7	$237.89	13.458%	$269.9052	$269.91	$269.90	$269.90
7 purchase totals =	$932.57		$1,018.0608	$1,018.07	$1,018.05	$1,018.00