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	$154.25	5.541%	$162.797	$162.80	$162.80	$162.80
Purchase #2	$194.46	7.205%	$208.4708	$208.47	$208.45	$208.50
Purchase #3	$170.41	5.178%	$179.2338	$179.23	$179.25	$179.20
Purchase #4	$216.31	11.559%	$241.3133	$241.31	$241.30	$241.30
Purchase #5	$79.89	10.746%	$88.475	$88.48	$88.50	$88.50
Purchase #6	$38.72	11.139%	$43.033	$43.03	$43.05	$43.00
Purchase #7	$174.60	4.807%	$182.993	$182.99	$183.00	$183.00
7 purchase totals =	$1,028.64		$1,106.3159	$1,106.31	$1,106.35	$1,106.30