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	$165.84	5.221%	$174.4985	$174.50	$174.50	$174.50
Purchase #2	$40.57	9.604%	$44.4663	$44.47	$44.45	$44.50
Purchase #3	$172.57	13.559%	$195.9688	$195.97	$195.95	$196.00
Purchase #4	$183.96	13.663%	$209.0945	$209.09	$209.10	$209.10
Purchase #5	$216.91	3.510%	$224.5235	$224.52	$224.50	$224.50
Purchase #6	$88.45	9.109%	$96.5069	$96.51	$96.50	$96.50
Purchase #7	$224.67	5.856%	$237.8267	$237.83	$237.85	$237.80
7 purchase totals =	$1,092.97		$1,182.8852	$1,182.89	$1,182.85	$1,182.90