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	$196.59	11.254%	$218.7142	$218.71	$218.70	$218.70
Purchase #2	$202.41	5.388%	$213.3159	$213.32	$213.30	$213.30
Purchase #3	$66.77	10.622%	$73.8623	$73.86	$73.85	$73.90
Purchase #4	$134.90	12.257%	$151.4347	$151.43	$151.45	$151.40
Purchase #5	$85.68	5.837%	$90.6811	$90.68	$90.70	$90.70
Purchase #6	$200.53	7.367%	$215.303	$215.30	$215.30	$215.30
Purchase #7	$50.58	7.484%	$54.3654	$54.37	$54.35	$54.40
7 purchase totals =	$937.46		$1,017.6766	$1,017.67	$1,017.65	$1,017.70