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	$96.51	7.420%	$103.671	$103.67	$103.65	$103.70
Purchase #2	$8.91	7.152%	$9.5472	$9.55	$9.55	$9.50
Purchase #3	$93.59	5.123%	$98.3846	$98.38	$98.40	$98.40
Purchase #4	$247.84	13.126%	$280.3715	$280.37	$280.35	$280.40
Purchase #5	$218.64	3.317%	$225.8923	$225.89	$225.90	$225.90
Purchase #6	$106.81	7.615%	$114.9436	$114.94	$114.95	$114.90
Purchase #7	$188.42	4.285%	$196.4938	$196.49	$196.50	$196.50
7 purchase totals =	$960.72		$1,029.3040	$1,029.29	$1,029.30	$1,029.30