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	$43.30	11.337%	$48.2089	$48.21	$48.20	$48.20
Purchase #2	$101.47	4.228%	$105.7602	$105.76	$105.75	$105.80
Purchase #3	$205.64	13.275%	$232.9387	$232.94	$232.95	$232.90
Purchase #4	$96.93	13.372%	$109.8915	$109.89	$109.90	$109.90
Purchase #5	$161.97	8.820%	$176.2558	$176.26	$176.25	$176.30
Purchase #6	$184.96	3.766%	$191.9256	$191.93	$191.95	$191.90
Purchase #7	$200.29	11.306%	$222.9348	$222.93	$222.95	$222.90
7 purchase totals =	$994.56		$1,087.9155	$1,087.92	$1,087.95	$1,087.90