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	$73.66	9.449%	$80.6201	$80.62	$80.60	$80.60
Purchase #2	$132.76	6.871%	$141.8819	$141.88	$141.90	$141.90
Purchase #3	$180.61	6.271%	$191.9361	$191.94	$191.95	$191.90
Purchase #4	$166.50	12.858%	$187.9086	$187.91	$187.90	$187.90
Purchase #5	$197.91	13.336%	$224.3033	$224.30	$224.30	$224.30
Purchase #6	$83.60	3.501%	$86.5268	$86.53	$86.55	$86.50
Purchase #7	$200.38	11.536%	$223.4958	$223.50	$223.50	$223.50
7 purchase totals =	$1,035.42		$1,136.6726	$1,136.68	$1,136.70	$1,136.60