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	$162.78	7.167%	$174.4464	$174.45	$174.45	$174.40
Purchase #2	$35.78	7.730%	$38.5458	$38.55	$38.55	$38.50
Purchase #3	$52.29	9.203%	$57.1022	$57.10	$57.10	$57.10
Purchase #4	$67.75	11.683%	$75.6652	$75.67	$75.65	$75.70
Purchase #5	$28.39	11.427%	$31.6341	$31.63	$31.65	$31.60
Purchase #6	$136.72	13.263%	$154.8532	$154.85	$154.85	$154.90
Purchase #7	$76.32	11.700%	$85.2494	$85.25	$85.25	$85.20
7 purchase totals =	$560.03		$617.4963	$617.50	$617.50	$617.40