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	$175.98	6.153%	$186.808	$186.81	$186.80	$186.80
Purchase #2	$239.89	6.634%	$255.8043	$255.80	$255.80	$255.80
Purchase #3	$28.39	11.559%	$31.6716	$31.67	$31.65	$31.70
Purchase #4	$84.31	7.238%	$90.4124	$90.41	$90.40	$90.40
Purchase #5	$190.55	12.772%	$214.887	$214.89	$214.90	$214.90
Purchase #6	$105.44	3.811%	$109.4583	$109.46	$109.45	$109.50
Purchase #7	$119.28	4.304%	$124.4138	$124.41	$124.40	$124.40
7 purchase totals =	$943.84		$1,013.4554	$1,013.45	$1,013.40	$1,013.50