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	$234.84	4.870%	$246.2767	$246.28	$246.30	$246.30
Purchase #2	$227.86	13.173%	$257.876	$257.88	$257.90	$257.90
Purchase #3	$166.88	3.747%	$173.133	$173.13	$173.15	$173.10
Purchase #4	$38.96	10.187%	$42.9289	$42.93	$42.95	$42.90
Purchase #5	$178.37	5.208%	$187.6595	$187.66	$187.65	$187.70
Purchase #6	$54.81	8.743%	$59.602	$59.60	$59.60	$59.60
Purchase #7	$39.88	8.421%	$43.2383	$43.24	$43.25	$43.20
7 purchase totals =	$941.60		$1,010.7144	$1,010.72	$1,010.80	$1,010.70