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	$82.86	11.679%	$92.5372	$92.54	$92.55	$92.50
Purchase #2	$210.96	6.454%	$224.5754	$224.58	$224.60	$224.60
Purchase #3	$52.63	12.556%	$59.2382	$59.24	$59.25	$59.20
Purchase #4	$82.77	11.513%	$92.2993	$92.30	$92.30	$92.30
Purchase #5	$32.84	5.333%	$34.5914	$34.59	$34.60	$34.60
Purchase #6	$17.75	3.277%	$18.3317	$18.33	$18.35	$18.30
Purchase #7	$11.46	13.459%	$13.0024	$13.00	$13.00	$13.00
7 purchase totals =	$491.27		$534.5756	$534.58	$534.65	$534.50