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	$175.49	3.710%	$182.0007	$182.00	$182.00	$182.00
Purchase #2	$201.30	6.146%	$213.6719	$213.67	$213.65	$213.70
Purchase #3	$184.96	6.108%	$196.2574	$196.26	$196.25	$196.30
Purchase #4	$166.46	13.236%	$188.4926	$188.49	$188.50	$188.50
Purchase #5	$100.85	8.466%	$109.388	$109.39	$109.40	$109.40
Purchase #6	$100.70	10.573%	$111.347	$111.35	$111.35	$111.30
Purchase #7	$15.71	12.581%	$17.6865	$17.69	$17.70	$17.70
7 purchase totals =	$945.47		$1,018.8441	$1,018.85	$1,018.85	$1,018.90