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	$226.27	6.446%	$240.8554	$240.86	$240.85	$240.90
Purchase #2	$25.59	3.292%	$26.4324	$26.43	$26.45	$26.40
Purchase #3	$183.63	10.840%	$203.5355	$203.54	$203.55	$203.50
Purchase #4	$158.31	11.494%	$176.5062	$176.51	$176.50	$176.50
Purchase #5	$65.29	9.651%	$71.5911	$71.59	$71.60	$71.60
Purchase #6	$152.36	8.280%	$164.9754	$164.98	$165.00	$165.00
Purchase #7	$238.85	7.339%	$256.3792	$256.38	$256.40	$256.40
7 purchase totals =	$1,050.30		$1,140.2752	$1,140.29	$1,140.35	$1,140.30