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	$181.78	10.317%	$200.5342	$200.53	$200.55	$200.50
Purchase #2	$194.59	13.764%	$221.3734	$221.37	$221.35	$221.40
Purchase #3	$144.61	12.316%	$162.4202	$162.42	$162.40	$162.40
Purchase #4	$117.40	11.664%	$131.0935	$131.09	$131.10	$131.10
Purchase #5	$126.29	4.721%	$132.2522	$132.25	$132.25	$132.30
Purchase #6	$148.51	11.707%	$165.8961	$165.90	$165.90	$165.90
Purchase #7	$14.36	6.767%	$15.3317	$15.33	$15.35	$15.30
7 purchase totals =	$927.54		$1,028.9013	$1,028.89	$1,028.90	$1,028.90