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	$44.60	6.597%	$47.5423	$47.54	$47.55	$47.50
Purchase #2	$55.84	6.853%	$59.6667	$59.67	$59.65	$59.70
Purchase #3	$245.61	4.502%	$256.6674	$256.67	$256.65	$256.70
Purchase #4	$220.39	13.844%	$250.9008	$250.90	$250.90	$250.90
Purchase #5	$208.89	11.654%	$233.234	$233.23	$233.25	$233.20
Purchase #6	$37.68	12.526%	$42.3998	$42.40	$42.40	$42.40
Purchase #7	$108.69	5.158%	$114.2962	$114.30	$114.30	$114.30
7 purchase totals =	$921.70		$1,004.7072	$1,004.71	$1,004.70	$1,004.70