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	$57.55	8.124%	$62.2254	$62.23	$62.25	$62.20
Purchase #2	$110.37	11.724%	$123.3098	$123.31	$123.30	$123.30
Purchase #3	$73.48	7.277%	$78.8271	$78.83	$78.85	$78.80
Purchase #4	$154.70	6.410%	$164.6163	$164.62	$164.60	$164.60
Purchase #5	$243.42	12.439%	$273.699	$273.70	$273.70	$273.70
Purchase #6	$157.91	13.356%	$179.0005	$179.00	$179.00	$179.00
Purchase #7	$247.79	3.102%	$255.4764	$255.48	$255.50	$255.50
7 purchase totals =	$1,045.22		$1,137.1545	$1,137.17	$1,137.20	$1,137.10