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	$113.25	10.467%	$125.1039	$125.10	$125.10	$125.10
Purchase #2	$57.47	3.217%	$59.3188	$59.32	$59.30	$59.30
Purchase #3	$167.75	5.383%	$176.78	$176.78	$176.80	$176.80
Purchase #4	$81.67	8.281%	$88.4331	$88.43	$88.45	$88.40
Purchase #5	$154.82	3.270%	$159.8826	$159.88	$159.90	$159.90
Purchase #6	$57.32	4.718%	$60.0244	$60.02	$60.00	$60.00
Purchase #7	$55.31	8.362%	$59.935	$59.94	$59.95	$59.90
7 purchase totals =	$687.59		$729.4778	$729.47	$729.50	$729.40