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	$245.44	13.508%	$278.594	$278.59	$278.60	$278.60
Purchase #2	$98.38	4.565%	$102.871	$102.87	$102.85	$102.90
Purchase #3	$212.75	11.333%	$236.861	$236.86	$236.85	$236.90
Purchase #4	$129.67	7.324%	$139.167	$139.17	$139.15	$139.20
Purchase #5	$175.89	11.476%	$196.0751	$196.08	$196.10	$196.10
Purchase #6	$64.70	12.688%	$72.9091	$72.91	$72.90	$72.90
Purchase #7	$118.94	13.372%	$134.8447	$134.84	$134.85	$134.80
7 purchase totals =	$1,045.77		$1,161.3219	$1,161.32	$1,161.30	$1,161.40