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	$210.71	6.718%	$224.8655	$224.87	$224.85	$224.90
Purchase #2	$109.40	12.541%	$123.1199	$123.12	$123.10	$123.10
Purchase #3	$234.94	3.166%	$242.3782	$242.38	$242.40	$242.40
Purchase #4	$185.86	10.641%	$205.6374	$205.64	$205.65	$205.60
Purchase #5	$38.52	5.853%	$40.7746	$40.77	$40.75	$40.80
Purchase #6	$163.73	13.319%	$185.5372	$185.54	$185.55	$185.50
Purchase #7	$106.72	5.563%	$112.6568	$112.66	$112.65	$112.70
7 purchase totals =	$1,049.88		$1,134.9696	$1,134.98	$1,134.95	$1,135.00