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	$213.71	4.354%	$223.0149	$223.01	$223.00	$223.00
Purchase #2	$38.64	10.424%	$42.6678	$42.67	$42.65	$42.70
Purchase #3	$161.66	13.375%	$183.282	$183.28	$183.30	$183.30
Purchase #4	$116.89	12.629%	$131.652	$131.65	$131.65	$131.70
Purchase #5	$62.59	8.243%	$67.7493	$67.75	$67.75	$67.70
Purchase #6	$179.56	9.555%	$196.717	$196.72	$196.70	$196.70
Purchase #7	$221.38	6.714%	$236.2435	$236.24	$236.25	$236.20
7 purchase totals =	$994.43		$1,081.3265	$1,081.32	$1,081.30	$1,081.30