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	$72.71	5.542%	$76.7396	$76.74	$76.75	$76.70
Purchase #2	$97.96	8.874%	$106.653	$106.65	$106.65	$106.70
Purchase #3	$174.83	12.309%	$196.3498	$196.35	$196.35	$196.30
Purchase #4	$109.64	3.449%	$113.4215	$113.42	$113.40	$113.40
Purchase #5	$242.89	9.643%	$266.3119	$266.31	$266.30	$266.30
Purchase #6	$221.99	3.524%	$229.8129	$229.81	$229.80	$229.80
Purchase #7	$100.67	10.629%	$111.3702	$111.37	$111.35	$111.40
7 purchase totals =	$1,020.69		$1,100.6589	$1,100.65	$1,100.60	$1,100.60