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	$13.30	8.320%	$14.4066	$14.41	$14.40	$14.40
Purchase #2	$203.90	13.407%	$231.2369	$231.24	$231.25	$231.20
Purchase #3	$181.59	3.419%	$187.7986	$187.80	$187.80	$187.80
Purchase #4	$38.51	9.848%	$42.3025	$42.30	$42.30	$42.30
Purchase #5	$159.85	9.604%	$175.202	$175.20	$175.20	$175.20
Purchase #6	$148.42	10.764%	$164.3959	$164.40	$164.40	$164.40
Purchase #7	$234.76	13.263%	$265.8962	$265.90	$265.90	$265.90
7 purchase totals =	$980.33		$1,081.2387	$1,081.25	$1,081.25	$1,081.20