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	$96.95	6.681%	$103.4272	$103.43	$103.45	$103.40
Purchase #2	$162.61	3.200%	$167.8135	$167.81	$167.80	$167.80
Purchase #3	$118.65	4.319%	$123.7745	$123.77	$123.75	$123.80
Purchase #4	$139.36	13.582%	$158.2879	$158.29	$158.30	$158.30
Purchase #5	$51.85	8.201%	$56.1022	$56.10	$56.10	$56.10
Purchase #6	$200.70	11.815%	$224.4127	$224.41	$224.40	$224.40
Purchase #7	$241.73	13.257%	$273.7761	$273.78	$273.80	$273.80
7 purchase totals =	$1,011.85		$1,107.5941	$1,107.59	$1,107.60	$1,107.60