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	$54.42	7.391%	$58.4422	$58.44	$58.45	$58.40
Purchase #2	$182.70	4.658%	$191.2102	$191.21	$191.20	$191.20
Purchase #3	$165.89	3.708%	$172.0412	$172.04	$172.05	$172.00
Purchase #4	$41.93	4.652%	$43.8806	$43.88	$43.90	$43.90
Purchase #5	$50.29	13.570%	$57.1144	$57.11	$57.10	$57.10
Purchase #6	$172.63	10.188%	$190.2175	$190.22	$190.20	$190.20
Purchase #7	$239.42	9.626%	$262.4666	$262.47	$262.45	$262.50
7 purchase totals =	$907.28		$975.3727	$975.37	$975.35	$975.30