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	$187.39	13.496%	$212.6802	$212.68	$212.70	$212.70
Purchase #2	$69.75	12.855%	$78.7164	$78.72	$78.70	$78.70
Purchase #3	$115.85	3.481%	$119.8827	$119.88	$119.90	$119.90
Purchase #4	$250.71	3.469%	$259.4071	$259.41	$259.40	$259.40
Purchase #5	$54.55	11.642%	$60.9007	$60.90	$60.90	$60.90
Purchase #6	$198.75	12.867%	$224.3232	$224.32	$224.30	$224.30
Purchase #7	$105.61	12.661%	$118.9813	$118.98	$119.00	$119.00
7 purchase totals =	$982.61		$1,074.8916	$1,074.89	$1,074.90	$1,074.90