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	$86.52	10.206%	$95.3502	$95.35	$95.35	$95.40
Purchase #2	$100.43	10.854%	$111.3307	$111.33	$111.35	$111.30
Purchase #3	$179.31	12.603%	$201.9084	$201.91	$201.90	$201.90
Purchase #4	$242.89	7.595%	$261.3375	$261.34	$261.35	$261.30
Purchase #5	$14.54	9.639%	$15.9415	$15.94	$15.95	$15.90
Purchase #6	$236.64	11.757%	$264.4618	$264.46	$264.45	$264.50
Purchase #7	$29.31	7.762%	$31.585	$31.59	$31.60	$31.60
7 purchase totals =	$889.64		$981.9151	$981.92	$981.95	$981.90