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	$93.72	4.322%	$97.7706	$97.77	$97.75	$97.80
Purchase #2	$65.53	3.481%	$67.8111	$67.81	$67.80	$67.80
Purchase #3	$106.80	11.619%	$119.2091	$119.21	$119.20	$119.20
Purchase #4	$153.97	7.512%	$165.5362	$165.54	$165.55	$165.50
Purchase #5	$182.44	4.663%	$190.9472	$190.95	$190.95	$190.90
Purchase #6	$118.86	10.635%	$131.5008	$131.50	$131.50	$131.50
Purchase #7	$217.57	9.673%	$238.6155	$238.62	$238.60	$238.60
7 purchase totals =	$938.89		$1,011.3905	$1,011.40	$1,011.35	$1,011.30